- 16 Nov, 2017 40 commits
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Michal Hocko authored
The preempt count check on print_vma_addr has been added by commit e8bff74a ("x86: fix "BUG: sleeping function called from invalid context" in print_vma_addr()") and it relied on the elevated preempt count from preempt_conditional_sti because preempt_count check doesn't work on non preemptive kernels by default. The code has evolved though and commit d99e1bd1 ("x86/entry/traps: Refactor preemption and interrupt flag handling") has replaced preempt_conditional_sti by an explicit preempt_disable which is noop on !PREEMPT so the check in print_vma_addr is broken. Fix the issue by using trylock on mmap_sem rather than chacking the preempt count. The allocation we are relying on has to be GFP_NOWAIT as well. There is a chance that we won't dump the vma state if the lock is contended or the memory short but this is acceptable outcome and much less fragile than the not working preemption check or tricks around it. Link: http://lkml.kernel.org/r/20171106134031.g6dbelg55mrbyc6i@dhcp22.suse.cz Fixes: d99e1bd1 ("x86/entry/traps: Refactor preemption and interrupt flag handling") Signed-off-by:
Michal Hocko <mhocko@suse.com> Acked-by:
Vlastimil Babka <vbabka@suse.cz> Acked-by:
Yang Shi <yang.s@alibaba-inc.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Michal Hocko authored
While doing memory hotplug tests under heavy memory pressure we have noticed too many page allocation failures when allocating vmemmap memmap backed by huge page kworker/u3072:1: page allocation failure: order:9, mode:0x24084c0(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO) [...] Call Trace: dump_trace+0x59/0x310 show_stack_log_lvl+0xea/0x170 show_stack+0x21/0x40 dump_stack+0x5c/0x7c warn_alloc_failed+0xe2/0x150 __alloc_pages_nodemask+0x3ed/0xb20 alloc_pages_current+0x7f/0x100 vmemmap_alloc_block+0x79/0xb6 __vmemmap_alloc_block_buf+0x136/0x145 vmemmap_populate+0xd2/0x2b9 sparse_mem_map_populate+0x23/0x30 sparse_add_one_section+0x68/0x18e __add_pages+0x10a/0x1d0 arch_add_memory+0x4a/0xc0 add_memory_resource+0x89/0x160 add_memory+0x6d/0xd0 acpi_memory_device_add+0x181/0x251 acpi_bus_attach+0xfd/0x19b acpi_bus_scan+0x59/0x69 acpi_device_hotplug+0xd2/0x41f acpi_hotplug_work_fn+0x1a/0x23 process_one_work+0x14e/0x410 worker_thread+0x116/0x490 kthread+0xbd/0xe0 ret_from_fork+0x3f/0x70 and we do see many of those because essentially every allocation fails for each memory section. This is an excessive way to tell the user that there is nothing to really worry about because we do have a fallback mechanism to use base pages. The only downside might be a performance degradation due to TLB pressure. This patch changes vmemmap_alloc_block() to use __GFP_NOWARN and warn explicitly once on the first allocation failure. This will reduce the noise in the kernel log considerably, while we still have an indication that a performance might be impacted. [mhocko@kernel.org: forgot to git add the follow up fix] Link: http://lkml.kernel.org/r/20171107090635.c27thtse2lchjgvb@dhcp22.suse.cz Link: http://lkml.kernel.org/r/20171106092228.31098-1-mhocko@kernel.orgSigned-off-by:Johannes Weiner <hannes@cmpxchg.org> Signed-off-by:
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Colin Ian King authored
Variable align_end is assigned a value but it is never read, so the variable is redundant and can be removed. Cleans up the clang warning: Value stored to 'align_end' is never read Link: http://lkml.kernel.org/r/20171017143837.23207-1-colin.king@canonical.comSigned-off-by:
Colin Ian King <colin.king@canonical.com> Reviewed-by:
Jérôme Glisse <jglisse@redhat.com> Signed-off-by:
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Gustavo A. R. Silva authored
In preparation for enabling -Wimplicit-fallthrough, mark switch cases where we are expecting to fall through. Link: http://lkml.kernel.org/r/20171020190754.GA24332@embeddedor.comSigned-off-by:
Gustavo A. R. Silva <garsilva@embeddedor.com> Signed-off-by:
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Gustavo A. R. Silva authored
In preparation to enabling -Wimplicit-fallthrough, mark switch cases where we are expecting to fall through. Link: http://lkml.kernel.org/r/20171020191058.GA24427@embeddedor.comSigned-off-by:
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Pavel Tatashin authored
In reset_deferred_meminit() we determine number of pages that must not be deferred. We initialize pages for at least 2G of memory, but also pages for reserved memory in this node. The reserved memory is determined in this function: memblock_reserved_memory_within(), which operates over physical addresses, and returns size in bytes. However, reset_deferred_meminit() assumes that that this function operates with pfns, and returns page count. The result is that in the best case machine boots slower than expected due to initializing more pages than needed in single thread, and in the worst case panics because fewer than needed pages are initialized early. Link: http://lkml.kernel.org/r/20171021011707.15191-1-pasha.tatashin@oracle.com Fixes: 864b9a39 ("mm: consider memblock reservations for deferred memory initialization sizing") Signed-off-by:
Pavel Tatashin <pasha.tatashin@oracle.com> Acked-by:
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Tetsuo Handa authored
Commit 63f53dea ("mm: warn about allocations which stall for too long") was a great step for reducing possibility of silent hang up problem caused by memory allocation stalls. But this commit reverts it, for it is possible to trigger OOM lockup and/or soft lockups when many threads concurrently called warn_alloc() (in order to warn about memory allocation stalls) due to current implementation of printk(), and it is difficult to obtain useful information due to limitation of synchronous warning approach. Current printk() implementation flushes all pending logs using the context of a thread which called console_unlock(). printk() should be able to flush all pending logs eventually unless somebody continues appending to printk() buffer. Since warn_alloc() started appending to printk() buffer while waiting for oom_kill_process() to make forward progress when oom_kill_process() is processing pending logs, it became possible for warn_alloc() to force oom_kill_process() loop inside printk(). As a result, warn_alloc() significantly increased possibility of preventing oom_kill_process() from making forward progress. ---------- Pseudo code start ---------- Before warn_alloc() was introduced: retry: if (mutex_trylock(&oom_lock)) { while (atomic_read(&printk_pending_logs) > 0) { atomic_dec(&printk_pending_logs); print_one_log(); } // Send SIGKILL here. mutex_unlock(&oom_lock) } goto retry; After warn_alloc() was introduced: retry: if (mutex_trylock(&oom_lock)) { while (atomic_read(&printk_pending_logs) > 0) { atomic_dec(&printk_pending_logs); print_one_log(); } // Send SIGKILL here. mutex_unlock(&oom_lock) } else if (waited_for_10seconds()) { atomic_inc(&printk_pending_logs); } goto retry; ---------- Pseudo code end ---------- Although waited_for_10seconds() becomes true once per 10 seconds, unbounded number of threads can call waited_for_10seconds() at the same time. Also, since threads doing waited_for_10seconds() keep doing almost busy loop, the thread doing print_one_log() can use little CPU resource. Therefore, this situation can be simplified like ---------- Pseudo code start ---------- retry: if (mutex_trylock(&oom_lock)) { while (atomic_read(&printk_pending_logs) > 0) { atomic_dec(&printk_pending_logs); print_one_log(); } // Send SIGKILL here. mutex_unlock(&oom_lock) } else { atomic_inc(&printk_pending_logs); } goto retry; ---------- Pseudo code end ---------- when printk() is called faster than print_one_log() can process a log. One of possible mitigation would be to introduce a new lock in order to make sure that no other series of printk() (either oom_kill_process() or warn_alloc()) can append to printk() buffer when one series of printk() (either oom_kill_process() or warn_alloc()) is already in progress. Such serialization will also help obtaining kernel messages in readable form. ---------- Pseudo code start ---------- retry: if (mutex_trylock(&oom_lock)) { mutex_lock(&oom_printk_lock); while (atomic_read(&printk_pending_logs) > 0) { atomic_dec(&printk_pending_logs); print_one_log(); } // Send SIGKILL here. mutex_unlock(&oom_printk_lock); mutex_unlock(&oom_lock) } else { if (mutex_trylock(&oom_printk_lock)) { atomic_inc(&printk_pending_logs); mutex_unlock(&oom_printk_lock); } } goto retry; ---------- Pseudo code end ---------- But this commit does not go that direction, for we don't want to introduce a new lock dependency, and we unlikely be able to obtain useful information even if we serialized oom_kill_process() and warn_alloc(). Synchronous approach is prone to unexpected results (e.g. too late [1], too frequent [2], overlooked [3]). As far as I know, warn_alloc() never helped with providing information other than "something is going wrong". I want to consider asynchronous approach which can obtain information during stalls with possibly relevant threads (e.g. the owner of oom_lock and kswapd-like threads) and serve as a trigger for actions (e.g. turn on/off tracepoints, ask libvirt daemon to take a memory dump of stalling KVM guest for diagnostic purpose). This commit temporarily loses ability to report e.g. OOM lockup due to unable to invoke the OOM killer due to !__GFP_FS allocation request. But asynchronous approach will be able to detect such situation and emit warning. Thus, let's remove warn_alloc(). [1] https://bugzilla.kernel.org/show_bug.cgi?id=192981 [2] http://lkml.kernel.org/r/CAM_iQpWuPVGc2ky8M-9yukECtS+zKjiDasNymX7rMcBjBFyM_A@mail.gmail.com [3] commit db73ee0d ("mm, vmscan: do not loop on too_many_isolated for ever")) Link: http://lkml.kernel.org/r/1509017339-4802-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jpSigned-off-by:
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by:
Cong Wang <xiyou.wangcong@gmail.com> Reported-by:
yuwang.yuwang <yuwang.yuwang@alibaba-inc.com> Reported-by:
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Johannes Weiner authored
Fuse inodes are currently included in the unreclaimable slab counts - SUnreclaim in /proc/meminfo, slab_unreclaimable in /proc/vmstat and the per-cgroup memory.stat. But they are reclaimable just like other filesystems' inodes, and /proc/sys/vm/drop_caches frees them easily. Mark the slab cache reclaimable. Link: http://lkml.kernel.org/r/20171102202727.12539-1-hannes@cmpxchg.orgSigned-off-by:
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Vlastimil Babka authored
Since commit 97a16fc8 ("mm, page_alloc: only enforce watermarks for order-0 allocations"), __zone_watermark_ok() check for high-order allocations will shortcut per-migratetype free list checks for ALLOC_HARDER allocations, and return true as long as there's free page of any migratetype. The intention is that ALLOC_HARDER can allocate from MIGRATE_HIGHATOMIC free lists, while normal allocations can't. However, as a side effect, the watermark check will then also return true when there are pages only on the MIGRATE_ISOLATE list, or (prior to CMA conversion to ZONE_MOVABLE) on the MIGRATE_CMA list. Since the allocation cannot actually obtain isolated pages, and might not be able to obtain CMA pages, this can result in a false positive. The condition should be rare and perhaps the outcome is not a fatal one. Still, it's better if the watermark check is correct. There also shouldn't be a performance tradeoff here. Link: http://lkml.kernel.org/r/20171102125001.23708-1-vbabka@suse.cz Fixes: 97a16fc8 ("mm, page_alloc: only enforce watermarks for order-0 allocations") Signed-off-by:
Mel Gorman <mgorman@techsingularity.net> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Rik van Riel <riel@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by:
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Shakeel Butt authored
lru_add_drain_all() is not required by mlock() and it will drain everything that has been cached at the time mlock is called. And that is not really related to the memory which will be faulted in (and cached) and mlocked by the syscall itself. If anything lru_add_drain_all() should be called _after_ pages have been mlocked and faulted in but even that is not strictly needed because those pages would get to the appropriate LRUs lazily during the reclaim path. Moreover follow_page_pte (gup) will drain the local pcp LRU cache. On larger machines the overhead of lru_add_drain_all() in mlock() can be significant when mlocking data already in memory. We have observed high latency in mlock() due to lru_add_drain_all() when the users were mlocking in memory tmpfs files. [mhocko@suse.com: changelog fix] Link: http://lkml.kernel.org/r/20171019222507.2894-1-shakeelb@google.comSigned-off-by:
Shakeel Butt <shakeelb@google.com> Acked-by:
Balbir Singh <bsingharora@gmail.com> Acked-by:
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Kemi Wang authored
This is the second step which introduces a tunable interface that allow numa stats configurable for optimizing zone_statistics(), as suggested by Dave Hansen and Ying Huang. ========================================================================= When page allocation performance becomes a bottleneck and you can tolerate some possible tool breakage and decreased numa counter precision, you can do: echo 0 > /proc/sys/vm/numa_stat In this case, numa counter update is ignored. We can see about *4.8%*(185->176) drop of cpu cycles per single page allocation and reclaim on Jesper's page_bench01 (single thread) and *8.1%*(343->315) drop of cpu cycles per single page allocation and reclaim on Jesper's page_bench03 (88 threads) running on a 2-Socket Broadwell-based server (88 threads, 126G memory). Benchmark link provided by Jesper D Brouer (increase loop times to 10000000): https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench ========================================================================= When page allocation performance is not a bottleneck and you want all tooling to work, you can do: echo 1 > /proc/sys/vm/numa_stat This is system default setting. Many thanks to Michal Hocko, Dave Hansen, Ying Huang and Vlastimil Babka for comments to help improve the original patch. [keescook@chromium.org: make sure mutex is a global static] Link: http://lkml.kernel.org/r/20171107213809.GA4314@beast Link: http://lkml.kernel.org/r/1508290927-8518-1-git-send-email-kemi.wang@intel.comSigned-off-by:
Kemi Wang <kemi.wang@intel.com> Signed-off-by:
Kees Cook <keescook@chromium.org> Reported-by:
Jesper Dangaard Brouer <brouer@redhat.com> Suggested-by:
Dave Hansen <dave.hansen@intel.com> Suggested-by:
Ying Huang <ying.huang@intel.com> Acked-by:
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weiping zhang authored
shmem_inode_cachep was created with SLAB_PANIC flag and shmem_init_inodecache() never returns non-zero, so convert this function to return void. Link: http://lkml.kernel.org/r/20170909124542.GA35224@bogon.didichuxing.comSigned-off-by:
weiping zhang <zhangweiping@didichuxing.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by:
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Otto Ebeling authored
Commit 197e7e52 ("Sanitize 'move_pages()' permission checks") fixed a security issue I reported in the move_pages syscall, and made it so that you can't act on set-uid processes unless you have the CAP_SYS_PTRACE capability. Unify the access check logic of migrate_pages to match the new behavior of move_pages. We discussed this a bit in the security@ list and thought it'd be good for consistency even though there's no evident security impact. The NUMA node access checks are left intact and require CAP_SYS_NICE as before. Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1710011830320.6333@lakka.kapsi.fiSigned-off-by:
Otto Ebeling <otto.ebeling@iki.fi> Acked-by:
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Mel Gorman authored
According to Vlastimil Babka, the drained field in pagevec is potentially misleading because it might be interpreted as draining this pagevec instead of the percpu lru pagevecs. Rename the field for clarity. Link: http://lkml.kernel.org/r/20171019093346.ylahzdpzmoriyf4v@techsingularity.netSigned-off-by:
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Vlastimil Babka authored
rmqueue_bulk() fills an empty pcplist with pages from the free list. It tries to preserve increasing order by pfn to the caller, because it leads to better performance with some I/O controllers, as explained in commit e084b2d9 ("page-allocator: preserve PFN ordering when __GFP_COLD is set"). To preserve the order, it's sufficient to add pages to the tail of the list as they are retrieved. The current code instead adds to the head of the list, but then updates the list head pointer to the last added page, in each step. This does result in the same order, but is needlessly confusing and potentially wasteful, with no apparent benefit. This patch simplifies the code and adjusts comment accordingly. Link: http://lkml.kernel.org/r/f6505442-98a9-12e4-b2cd-0fa83874c159@suse.czSigned-off-by:
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Mel Gorman authored
As the page free path makes no distinction between cache hot and cold pages, there is no real useful ordering of pages in the free list that allocation requests can take advantage of. Juding from the users of __GFP_COLD, it is likely that a number of them are the result of copying other sites instead of actually measuring the impact. Remove the __GFP_COLD parameter which simplifies a number of paths in the page allocator. This is potentially controversial but bear in mind that the size of the per-cpu pagelists versus modern cache sizes means that the whole per-cpu list can often fit in the L3 cache. Hence, there is only a potential benefit for microbenchmarks that alloc/free pages in a tight loop. It's even worse when THP is taken into account which has little or no chance of getting a cache-hot page as the per-cpu list is bypassed and the zeroing of multiple pages will thrash the cache anyway. The truncate microbenchmarks are not shown as this patch affects the allocation path and not the free path. A page fault microbenchmark was tested but it showed no sigificant difference which is not surprising given that the __GFP_COLD branches are a miniscule percentage of the fault path. Link: http://lkml.kernel.org/r/20171018075952.10627-9-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
Most callers users of free_hot_cold_page claim the pages being released are cache hot. The exception is the page reclaim paths where it is likely that enough pages will be freed in the near future that the per-cpu lists are going to be recycled and the cache hotness information is lost. As no one really cares about the hotness of pages being released to the allocator, just ditch the parameter. The APIs are renamed to indicate that it's no longer about hot/cold pages. It should also be less confusing as there are subtle differences between them. __free_pages drops a reference and frees a page when the refcount reaches zero. free_hot_cold_page handled pages whose refcount was already zero which is non-obvious from the name. free_unref_page should be more obvious. No performance impact is expected as the overhead is marginal. The parameter is removed simply because it is a bit stupid to have a useless parameter copied everywhere. [mgorman@techsingularity.net: add pages to head, not tail] Link: http://lkml.kernel.org/r/20171019154321.qtpzaeftoyyw4iey@techsingularity.net Link: http://lkml.kernel.org/r/20171018075952.10627-8-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
All callers of release_pages claim the pages being released are cache hot. As no one cares about the hotness of pages being released to the allocator, just ditch the parameter. No performance impact is expected as the overhead is marginal. The parameter is removed simply because it is a bit stupid to have a useless parameter copied everywhere. Link: http://lkml.kernel.org/r/20171018075952.10627-7-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
Every pagevec_init user claims the pages being released are hot even in cases where it is unlikely the pages are hot. As no one cares about the hotness of pages being released to the allocator, just ditch the parameter. No performance impact is expected as the overhead is marginal. The parameter is removed simply because it is a bit stupid to have a useless parameter copied everywhere. Link: http://lkml.kernel.org/r/20171018075952.10627-6-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
When a pagevec is initialised on the stack, it is generally used multiple times over a range of pages, looking up entries and then releasing them. On each pagevec_release, the per-cpu deferred LRU pagevecs are drained on the grounds the page being released may be on those queues and the pages may be cache hot. In many cases only the first drain is necessary as it's unlikely that the range of pages being walked is racing against LRU addition. Even if there is such a race, the impact is marginal where as constantly redraining the lru pagevecs costs. This patch ensures that pagevec is only drained once in a given lifecycle without increasing the cache footprint of the pagevec structure. Only sparsetruncate tiny is shown here as large files have many exceptional entries and calls pagecache_release less frequently. sparsetruncate (tiny) 4.14.0-rc4 4.14.0-rc4 batchshadow-v1r1 onedrain-v1r1 Min Time 141.00 ( 0.00%) 141.00 ( 0.00%) 1st-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%) 2nd-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%) 3rd-qrtle Time 143.00 ( 0.00%) 143.00 ( 0.00%) Max-90% Time 144.00 ( 0.00%) 144.00 ( 0.00%) Max-95% Time 146.00 ( 0.00%) 145.00 ( 0.68%) Max-99% Time 198.00 ( 0.00%) 194.00 ( 2.02%) Max Time 254.00 ( 0.00%) 208.00 ( 18.11%) Amean Time 145.12 ( 0.00%) 144.30 ( 0.56%) Stddev Time 12.74 ( 0.00%) 9.62 ( 24.49%) Coeff Time 8.78 ( 0.00%) 6.67 ( 24.06%) Best99%Amean Time 144.29 ( 0.00%) 143.82 ( 0.32%) Best95%Amean Time 142.68 ( 0.00%) 142.31 ( 0.26%) Best90%Amean Time 142.52 ( 0.00%) 142.19 ( 0.24%) Best75%Amean Time 142.26 ( 0.00%) 141.98 ( 0.20%) Best50%Amean Time 141.90 ( 0.00%) 141.71 ( 0.13%) Best25%Amean Time 141.80 ( 0.00%) 141.43 ( 0.26%) The impact on bonnie is marginal and within the noise because a significant percentage of the file being truncated has been reclaimed and consists of shadow entries which reduce the hotness of the pagevec_release path. Link: http://lkml.kernel.org/r/20171018075952.10627-5-mgorman@techsingularity.netSigned-off-by: -
Mel Gorman authored
During truncate each entry in a pagevec is checked to see if it is an exceptional entry and if so, the shadow entry is cleaned up. This is potentially expensive as multiple entries for a mapping locks/unlocks the tree lock. This batches the operation such that any exceptional entries removed from a pagevec only acquire the mapping tree lock once. The corner case where this is more expensive is where there is only one exceptional entry but this is unlikely due to temporal locality and how it affects LRU ordering. Note that for truncations of small files created recently, this patch should show no gain because it only batches the handling of exceptional entries. sparsetruncate (large) 4.14.0-rc4 4.14.0-rc4 pickhelper-v1r1 batchshadow-v1r1 Min Time 38.00 ( 0.00%) 27.00 ( 28.95%) 1st-qrtle Time 40.00 ( 0.00%) 28.00 ( 30.00%) 2nd-qrtle Time 44.00 ( 0.00%) 41.00 ( 6.82%) 3rd-qrtle Time 146.00 ( 0.00%) 147.00 ( -0.68%) Max-90% Time 153.00 ( 0.00%) 153.00 ( 0.00%) Max-95% Time 155.00 ( 0.00%) 156.00 ( -0.65%) Max-99% Time 181.00 ( 0.00%) 171.00 ( 5.52%) Amean Time 93.04 ( 0.00%) 88.43 ( 4.96%) Best99%Amean Time 92.08 ( 0.00%) 86.13 ( 6.46%) Best95%Amean Time 89.19 ( 0.00%) 83.13 ( 6.80%) Best90%Amean Time 85.60 ( 0.00%) 79.15 ( 7.53%) Best75%Amean Time 72.95 ( 0.00%) 65.09 ( 10.78%) Best50%Amean Time 39.86 ( 0.00%) 28.20 ( 29.25%) Best25%Amean Time 39.44 ( 0.00%) 27.70 ( 29.77%) bonnie 4.14.0-rc4 4.14.0-rc4 pickhelper-v1r1 batchshadow-v1r1 Hmean SeqCreate ops 71.92 ( 0.00%) 76.78 ( 6.76%) Hmean SeqCreate read 42.42 ( 0.00%) 45.01 ( 6.10%) Hmean SeqCreate del 26519.88 ( 0.00%) 27191.87 ( 2.53%) Hmean RandCreate ops 71.92 ( 0.00%) 76.95 ( 7.00%) Hmean RandCreate read 44.44 ( 0.00%) 49.23 ( 10.78%) Hmean RandCreate del 24948.62 ( 0.00%) 24764.97 ( -0.74%) Truncation of a large number of files shows a substantial gain with 99% of files being truncated 6.46% faster. bonnie shows a modest gain of 2.53% [jack@suse.cz: fix truncate_exceptional_pvec_entries()] Link: http://lkml.kernel.org/r/20171108164226.26788-1-jack@suse.cz Link: http://lkml.kernel.org/r/20171018075952.10627-4-mgorman@techsingularity.netSigned-off-by:Jan Kara <jack@suse.cz> Reviewed-by:
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Mel Gorman authored
During truncation, the mapping has already been checked for shmem and dax so it's known that workingset_update_node is required. This patch avoids the checks on mapping for each page being truncated. In all other cases, a lookup helper is used to determine if workingset_update_node() needs to be called. The one danger is that the API is slightly harder to use as calling workingset_update_node directly without checking for dax or shmem mappings could lead to surprises. However, the API rarely needs to be used and hopefully the comment is enough to give people the hint. sparsetruncate (tiny) 4.14.0-rc4 4.14.0-rc4 oneirq-v1r1 pickhelper-v1r1 Min Time 141.00 ( 0.00%) 140.00 ( 0.71%) 1st-qrtle Time 142.00 ( 0.00%) 141.00 ( 0.70%) 2nd-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%) 3rd-qrtle Time 143.00 ( 0.00%) 143.00 ( 0.00%) Max-90% Time 144.00 ( 0.00%) 144.00 ( 0.00%) Max-95% Time 147.00 ( 0.00%) 145.00 ( 1.36%) Max-99% Time 195.00 ( 0.00%) 191.00 ( 2.05%) Max Time 230.00 ( 0.00%) 205.00 ( 10.87%) Amean Time 144.37 ( 0.00%) 143.82 ( 0.38%) Stddev Time 10.44 ( 0.00%) 9.00 ( 13.74%) Coeff Time 7.23 ( 0.00%) 6.26 ( 13.41%) Best99%Amean Time 143.72 ( 0.00%) 143.34 ( 0.26%) Best95%Amean Time 142.37 ( 0.00%) 142.00 ( 0.26%) Best90%Amean Time 142.19 ( 0.00%) 141.85 ( 0.24%) Best75%Amean Time 141.92 ( 0.00%) 141.58 ( 0.24%) Best50%Amean Time 141.69 ( 0.00%) 141.31 ( 0.27%) Best25%Amean Time 141.38 ( 0.00%) 140.97 ( 0.29%) As you'd expect, the gain is marginal but it can be detected. The differences in bonnie are all within the noise which is not surprising given the impact on the microbenchmark. radix_tree_update_node_t is a callback for some radix operations that optionally passes in a private field. The only user of the callback is workingset_update_node and as it no longer requires a mapping, the private field is removed. Link: http://lkml.kernel.org/r/20171018075952.10627-3-mgorman@techsingularity.netSigned-off-by: -
Mel Gorman authored
Patch series "Follow-up for speed up page cache truncation", v2. This series is a follow-on for Jan Kara's series "Speed up page cache truncation" series. We both ended up looking at the same problem but saw different problems based on the same data. This series builds upon his work. A variety of workloads were compared on four separate machines but each machine showed gains albeit at different levels. Minimally, some of the differences are due to NUMA where truncating data from a remote node is slower than a local node. The workloads checked were o sparse truncate microbenchmark, tiny o sparse truncate microbenchmark, large o reaim-io disk workfile o dbench4 (modified by mmtests to produce more stable results) o filebench varmail configuration for small memory size o bonnie, directory operations, working set size 2*RAM reaim-io, dbench and filebench all showed minor gains. Truncation does not dominate those workloads but were tested to ensure no other regressions. They will not be reported further. The sparse truncate microbench was written by Jan. It creates a number of files and then times how long it takes to truncate each one. The "tiny" configuraiton creates a number of files that easily fits in memory and times how long it takes to truncate files with page cache. The large configuration uses enough files to have data that is twice the size of memory and so timings there include truncating page cache and working set shadow entries in the radix tree. Patches 1-4 are the most relevant parts of this series. Patches 5-8 are optional as they are deleting code that is essentially useless but has a negligible performance impact. The changelogs have more information on performance but just for bonnie delete options, the main comparison is bonnie 4.14.0-rc5 4.14.0-rc5 4.14.0-rc5 jan-v2 vanilla mel-v2 Hmean SeqCreate ops 76.20 ( 0.00%) 75.80 ( -0.53%) 76.80 ( 0.79%) Hmean SeqCreate read 85.00 ( 0.00%) 85.00 ( 0.00%) 85.00 ( 0.00%) Hmean SeqCreate del 13752.31 ( 0.00%) 12090.23 ( -12.09%) 15304.84 ( 11.29%) Hmean RandCreate ops 76.00 ( 0.00%) 75.60 ( -0.53%) 77.00 ( 1.32%) Hmean RandCreate read 96.80 ( 0.00%) 96.80 ( 0.00%) 97.00 ( 0.21%) Hmean RandCreate del 13233.75 ( 0.00%) 11525.35 ( -12.91%) 14446.61 ( 9.16%) Jan's series is the baseline and the vanilla kernel is 12% slower where as this series on top gains another 11%. This is from a different machine than the data in the changelogs but the detailed data was not collected as there was no substantial change in v2. This patch (of 8): Freeing a list of pages current enables/disables IRQs for each page freed. This patch splits freeing a list of pages into two operations -- preparing the pages for freeing and the actual freeing. This is a tradeoff - we're taking two passes of the list to free in exchange for avoiding multiple enable/disable of IRQs. sparsetruncate (tiny) 4.14.0-rc4 4.14.0-rc4 janbatch-v1r1 oneirq-v1r1 Min Time 149.00 ( 0.00%) 141.00 ( 5.37%) 1st-qrtle Time 150.00 ( 0.00%) 142.00 ( 5.33%) 2nd-qrtle Time 151.00 ( 0.00%) 142.00 ( 5.96%) 3rd-qrtle Time 151.00 ( 0.00%) 143.00 ( 5.30%) Max-90% Time 153.00 ( 0.00%) 144.00 ( 5.88%) Max-95% Time 155.00 ( 0.00%) 147.00 ( 5.16%) Max-99% Time 201.00 ( 0.00%) 195.00 ( 2.99%) Max Time 236.00 ( 0.00%) 230.00 ( 2.54%) Amean Time 152.65 ( 0.00%) 144.37 ( 5.43%) Stddev Time 9.78 ( 0.00%) 10.44 ( -6.72%) Coeff Time 6.41 ( 0.00%) 7.23 ( -12.84%) Best99%Amean Time 152.07 ( 0.00%) 143.72 ( 5.50%) Best95%Amean Time 150.75 ( 0.00%) 142.37 ( 5.56%) Best90%Amean Time 150.59 ( 0.00%) 142.19 ( 5.58%) Best75%Amean Time 150.36 ( 0.00%) 141.92 ( 5.61%) Best50%Amean Time 150.04 ( 0.00%) 141.69 ( 5.56%) Best25%Amean Time 149.85 ( 0.00%) 141.38 ( 5.65%) With a tiny number of files, each file truncated has resident page cache and it shows that time to truncate is roughtly 5-6% with some minor jitter. 4.14.0-rc4 4.14.0-rc4 janbatch-v1r1 oneirq-v1r1 Hmean SeqCreate ops 65.27 ( 0.00%) 81.86 ( 25.43%) Hmean SeqCreate read 39.48 ( 0.00%) 47.44 ( 20.16%) Hmean SeqCreate del 24963.95 ( 0.00%) 26319.99 ( 5.43%) Hmean RandCreate ops 65.47 ( 0.00%) 82.01 ( 25.26%) Hmean RandCreate read 42.04 ( 0.00%) 51.75 ( 23.09%) Hmean RandCreate del 23377.66 ( 0.00%) 23764.79 ( 1.66%) As expected, there is a small gain for the delete operation. [mgorman@techsingularity.net: use page_private and set_page_private helpers] Link: http://lkml.kernel.org/r/20171018101547.mjycw7zreb66jzpa@techsingularity.net Link: http://lkml.kernel.org/r/20171018075952.10627-2-mgorman@techsingularity.netSigned-off-by: -
Jan Kara authored
Currently we remove pages from the radix tree one by one. To speed up page cache truncation, lock several pages at once and free them in one go. This allows us to batch radix tree operations in a more efficient way and also save round-trips on mapping->tree_lock. As a result we gain about 20% speed improvement in page cache truncation. Data from a simple benchmark timing 10000 truncates of 1024 pages (on ext4 on ramdisk but the filesystem is barely visible in the profiles). The range shows 1% and 95% percentiles of the measured times: 4.14-rc2 4.14-rc2 + batched truncation 248-256 209-219 249-258 209-217 248-255 211-239 248-255 209-217 247-256 210-218 [jack@suse.cz: convert delete_from_page_cache_batch() to pagevec] Link: http://lkml.kernel.org/r/20171018111648.13714-1-jack@suse.cz [akpm@linux-foundation.org: move struct pagevec forward declaration to top-of-file] Link: http://lkml.kernel.org/r/20171010151937.26984-8-jack@suse.czSigned-off-by:
Mel Gorman <mgorman@suse.de> Reviewed-by:
Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by:
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Jan Kara authored
Move checks and accounting updates from __delete_from_page_cache() into a separate function. We will reuse it when batching page cache truncation operations. Link: http://lkml.kernel.org/r/20171010151937.26984-7-jack@suse.czSigned-off-by:
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Jan Kara authored
Clearing of page->mapping makes sense in page_cache_tree_delete() as well and it will help us with batching things this way. Link: http://lkml.kernel.org/r/20171010151937.26984-6-jack@suse.czSigned-off-by:
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Jan Kara authored
Move updates of various counters before page_cache_tree_delete() call. It will be easier to batch things this way and there is no difference whether the counters get updated before or after removal from the radix tree. Link: http://lkml.kernel.org/r/20171010151937.26984-5-jack@suse.czSigned-off-by:
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Jan Kara authored
Factor out page freeing from delete_from_page_cache() into a separate function. We will need to call the same when batching pagecache deletion operations. invalidate_complete_page2() and replace_page_cache_page() might want to call this function as well however they currently don't seem to handle THPs so it's unnecessary for them to take the hit of checking whether a page is THP or not. Link: http://lkml.kernel.org/r/20171010151937.26984-4-jack@suse.czSigned-off-by:
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Jan Kara authored
Move call of delete_from_page_cache() and page->mapping check out of truncate_complete_page() into the single caller - truncate_inode_page(). Also move page_mapped() check into truncate_complete_page(). That way it will be easier to batch operations. Also rename truncate_complete_page() to truncate_cleanup_page(). Link: http://lkml.kernel.org/r/20171010151937.26984-3-jack@suse.czSigned-off-by:
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Jan Kara authored
Patch series "Speed up page cache truncation", v1. When rebasing our enterprise distro to a newer kernel (from 4.4 to 4.12) we have noticed a regression in bonnie++ benchmark when deleting files. Eventually we have tracked this down to a fact that page cache truncation got slower by about 10%. There were both gains and losses in the above interval of kernels but we have been able to identify that commit 83929372 ("filemap: prepare find and delete operations for huge pages") caused about 10% regression on its own. After some investigation it didn't seem easily possible to fix the regression while maintaining the THP in page cache functionality so we've decided to optimize the page cache truncation path instead to make up for the change. This series is a result of that effort. Patch 1 is an easy speedup of cancel_dirty_page(). Patches 2-6 refactor page cache truncation code so that it is easier to batch radix tree operations. Patch 7 implements batching of deletes from the radix tree which more than makes up for the original regression. This patch (of 7): cancel_dirty_page() does quite some work even for clean pages (fetching of mapping, locking of memcg, atomic bit op on page flags) so it accounts for ~2.5% of cost of truncation of a clean page. That is not much but still dumb for something we don't need at all. Check whether a page is actually dirty and avoid any work if not. Link: http://lkml.kernel.org/r/20171010151937.26984-2-jack@suse.czSigned-off-by:
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Colin Ian King authored
zram_page_end_io() is local to the source and does not need to be in global scope, so make it static. Cleans up sparse warning: symbol 'zram_page_end_io' was not declared. Should it be static? Link: http://lkml.kernel.org/r/20171016173336.20320-1-colin.king@canonical.comSigned-off-by:
Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by:
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Kees Cook authored
In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly. Link: http://lkml.kernel.org/r/20171016225913.GA99214@beastSigned-off-by:
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Laszlo Toth authored
On a failed attempt, we get the following entry: soft offline: 0x3c0000: migration failed 1, type 17ffffc0008008 (uptodate|head) Make this more specific to be straightforward and to follow other error log formats in soft_offline_huge_page(). Link: http://lkml.kernel.org/r/20171016171757.GA3018@ubuntu-desk-vmSigned-off-by:
Laszlo Toth <laszlth@gmail.com> Acked-by:
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by:
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Mike Rapoport authored
Link: http://lkml.kernel.org/r/1508132478-7738-1-git-send-email-rppt@linux.vnet.ibm.comSigned-off-by:
Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by:
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Aaron Lu authored
__rmqueue(), __rmqueue_fallback(), __rmqueue_smallest() and __rmqueue_cma_fallback() are all in page allocator's hot path and better be finished as soon as possible. One way to make them faster is by making them inline. But as Andrew Morton and Andi Kleen pointed out: https://lkml.org/lkml/2017/10/10/1252 https://lkml.org/lkml/2017/10/10/1279 To make sure they are inlined, we should use __always_inline for them. With the will-it-scale/page_fault1/process benchmark, when using nr_cpu processes to stress buddy, the results for will-it-scale.processes with and without the patch are: On a 2-sockets Intel-Skylake machine: compiler base head gcc-4.4.7 6496131 6911823 +6.4% gcc-4.9.4 7225110 7731072 +7.0% gcc-5.4.1 7054224 7688146 +9.0% gcc-6.2.0 7059794 7651675 +8.4% On a 4-sockets Intel-Skylake machine: compiler base head gcc-4.4.7 13162890 13508193 +2.6% gcc-4.9.4 14997463 15484353 +3.2% gcc-5.4.1 14708711 15449805 +5.0% gcc-6.2.0 14574099 15349204 +5.3% The above 4 compilers are used because I've done the tests through Intel's Linux Kernel Performance(LKP) infrastructure and they are the available compilers there. The benefit being less on 4 sockets machine is due to the lock contention there(perf-profile/native_queued_spin_lock_slowpath=81%) is less severe than on the 2 sockets machine(85%). What the benchmark does is: it forks nr_cpu processes and then each process does the following: 1 mmap() 128M anonymous space; 2 writes to each page there to trigger actual page allocation; 3 munmap() it. in a loop. https://github.com/antonblanchard/will-it-scale/blob/master/tests/page_fault1.c Binary size wise, I have locally built them with different compilers: [aaron@aaronlu obj]$ size */*/mm/page_alloc.o text data bss dec hex filename 37409 9904 8524 55837 da1d gcc-4.9.4/base/mm/page_alloc.o 38273 9904 8524 56701 dd7d gcc-4.9.4/head/mm/page_alloc.o 37465 9840 8428 55733 d9b5 gcc-5.5.0/base/mm/page_alloc.o 38169 9840 8428 56437 dc75 gcc-5.5.0/head/mm/page_alloc.o 37573 9840 8428 55841 da21 gcc-6.4.0/base/mm/page_alloc.o 38261 9840 8428 56529 dcd1 gcc-6.4.0/head/mm/page_alloc.o 36863 9840 8428 55131 d75b gcc-7.2.0/base/mm/page_alloc.o 37711 9840 8428 55979 daab gcc-7.2.0/head/mm/page_alloc.o Text size increased about 800 bytes for mm/page_alloc.o. [aaron@aaronlu obj]$ size */*/vmlinux text data bss dec hex filename 10342757 5903208 17723392 33969357 20654cd gcc-4.9.4/base/vmlinux 10342757 5903208 17723392 33969357 20654cd gcc-4.9.4/head/vmlinux 10332448 5836608 17715200 33884256 2050860 gcc-5.5.0/base/vmlinux 10332448 5836608 17715200 33884256 2050860 gcc-5.5.0/head/vmlinux 10094546 5836696 17715200 33646442 201676a gcc-6.4.0/base/vmlinux 10094546 5836696 17715200 33646442 201676a gcc-6.4.0/head/vmlinux 10018775 5828732 17715200 33562707 2002053 gcc-7.2.0/base/vmlinux 10018775 5828732 17715200 33562707 2002053 gcc-7.2.0/head/vmlinux Text size for vmlinux has no change though, probably due to function alignment. Link: http://lkml.kernel.org/r/20171013063111.GA26032@intel.comSigned-off-by:
Aaron Lu <aaron.lu@intel.com> Acked-by:
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Pavel Tatashin authored
Add an optimized mm_zero_struct_page(), so struct page's are zeroed without calling memset(). We do eight to ten regular stores based on the size of struct page. Compiler optimizes out the conditions of switch() statement. SPARC-M6 with 15T of memory, single thread performance: BASE FIX OPTIMIZED_FIX bootmem_init 28.440467985s 2.305674818s 2.305161615s free_area_init_nodes 202.845901673s 225.343084508s 172.556506560s -------------------------------------------- Total 231.286369658s 227.648759326s 174.861668175s BASE: current linux FIX: This patch series without "optimized struct page zeroing" OPTIMIZED_FIX: This patch series including the current patch. bootmem_init() is where memory for struct pages is zeroed during allocation. Note, about two seconds in this function is a fixed time: it does not increase as memory is increased. Link: http://lkml.kernel.org/r/20171013173214.27300-11-pasha.tatashin@oracle.comSigned-off-by:Steven Sistare <steven.sistare@oracle.com> Reviewed-by:
Daniel Jordan <daniel.m.jordan@oracle.com> Reviewed-by:
Bob Picco <bob.picco@oracle.com> Acked-by:
David S. Miller <davem@davemloft.net> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by:
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Pavel Tatashin authored
vmemmap_alloc_block() will no longer zero the block, so zero memory at its call sites for everything except struct pages. Struct page memory is zero'd by struct page initialization. Replace allocators in sparse-vmemmap to use the non-zeroing version. So, we will get the performance improvement by zeroing the memory in parallel when struct pages are zeroed. Add struct page zeroing as a part of initialization of other fields in __init_single_page(). This single thread performance collected on: Intel(R) Xeon(R) CPU E7-8895 v3 @ 2.60GHz with 1T of memory (268400646 pages in 8 nodes): BASE FIX sparse_init 11.244671836s 0.007199623s zone_sizes_init 4.879775891s 8.355182299s -------------------------- Total 16.124447727s 8.362381922s sparse_init is where memory for struct pages is zeroed, and the zeroing part is moved later in this patch into __init_single_page(), which is called from zone_sizes_init(). [akpm@linux-foundation.org: make vmemmap_alloc_block_zero() private to sparse-vmemmap.c] Link: http://lkml.kernel.org/r/20171013173214.27300-10-pasha.tatashin@oracle.comSigned-off-by: -
Will Deacon authored
The kasan shadow is currently mapped using vmemmap_populate() since that provides a semi-convenient way to map pages into init_top_pgt. However, since that no longer zeroes the mapped pages, it is not suitable for kasan, which requires zeroed shadow memory. Add kasan_populate_shadow() interface and use it instead of vmemmap_populate(). Besides, this allows us to take advantage of gigantic pages and use them to populate the shadow, which should save us some memory wasted on page tables and reduce TLB pressure. Link: http://lkml.kernel.org/r/20171103185147.2688-3-pasha.tatashin@oracle.comSigned-off-by:
Will Deacon <will.deacon@arm.com> Signed-off-by:
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Andrey Ryabinin authored
The kasan shadow is currently mapped using vmemmap_populate() since that provides a semi-convenient way to map pages into init_top_pgt. However, since that no longer zeroes the mapped pages, it is not suitable for kasan, which requires zeroed shadow memory. Add kasan_populate_shadow() interface and use it instead of vmemmap_populate(). Besides, this allows us to take advantage of gigantic pages and use them to populate the shadow, which should save us some memory wasted on page tables and reduce TLB pressure. Link: http://lkml.kernel.org/r/20171103185147.2688-2-pasha.tatashin@oracle.comSigned-off-by:
Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by:
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Pavel Tatashin authored
Some memory is reserved but unavailable: not present in memblock.memory (because not backed by physical pages), but present in memblock.reserved. Such memory has backing struct pages, but they are not initialized by going through __init_single_page(). In some cases these struct pages are accessed even if they do not contain any data. One example is page_to_pfn() might access page->flags if this is where section information is stored (CONFIG_SPARSEMEM, SECTION_IN_PAGE_FLAGS). One example of such memory: trim_low_memory_range() unconditionally reserves from pfn 0, but e820__memblock_setup() might provide the exiting memory from pfn 1 (i.e. KVM). Since struct pages are zeroed in __init_single_page(), and not during allocation time, we must zero such struct pages explicitly. The patch involves adding a new memblock iterator: for_each_resv_unavail_range(i, p_start, p_end) Which iterates through reserved && !memory lists, and we zero struct pages explicitly by calling mm_zero_struct_page(). === Here is more detailed example of problem that this patch is addressing: Run tested on qemu with the following arguments: -enable-kvm -cpu kvm64 -m 512 -smp 2 This patch reports that there are 98 unavailable pages. They are: pfn 0 and pfns in range [159, 255]. Note, trim_low_memory_range() reserves only pfns in range [0, 15], it does not reserve [159, 255] ones. e820__memblock_setup() reports linux that the following physical ranges are available: [1 , 158] [256, 130783] Notice, that exactly unavailable pfns are missing! Now, lets check what we have in zone 0: [1, 131039] pfn 0, is not part of the zone, but pfns [1, 158], are. However, the bigger problem we have if we do not initialize these struct pages is with memory hotplug. Because, that path operates at 2M boundaries (section_nr). And checks if 2M range of pages is hot removable. It starts with first pfn from zone, rounds it down to 2M boundary (sturct pages are allocated at 2M boundaries when vmemmap is created), and checks if that section is hot removable. In this case start with pfn 1 and convert it down to pfn 0. Later pfn is converted to struct page, and some fields are checked. Now, if we do not zero struct pages, we get unpredictable results. In fact when CONFIG_VM_DEBUG is enabled, and we explicitly set all vmemmap memory to ones, the following panic is observed with kernel test without this patch applied: BUG: unable to handle kernel NULL pointer dereference at (null) IP: is_pageblock_removable_nolock+0x35/0x90 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT ... task: ffff88001f4e2900 task.stack: ffffc90000314000 RIP: 0010:is_pageblock_removable_nolock+0x35/0x90 Call Trace: ? is_mem_section_removable+0x5a/0xd0 show_mem_removable+0x6b/0xa0 dev_attr_show+0x1b/0x50 sysfs_kf_seq_show+0xa1/0x100 kernfs_seq_show+0x22/0x30 seq_read+0x1ac/0x3a0 kernfs_fop_read+0x36/0x190 ? security_file_permission+0x90/0xb0 __vfs_read+0x16/0x30 vfs_read+0x81/0x130 SyS_read+0x44/0xa0 entry_SYSCALL_64_fastpath+0x1f/0xbd Link: http://lkml.kernel.org/r/20171013173214.27300-7-pasha.tatashin@oracle.comSigned-off-by:
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