- 26 Jul, 2016 40 commits
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Michal Hocko authored
Tetsuo is worried that mmput_async might still lead to a premature new oom victim selection due to the following race: __oom_reap_task exit_mm find_lock_task_mm atomic_inc(mm->mm_users) # = 2 task_unlock task_lock task->mm = NULL up_read(&mm->mmap_sem) < somebody write locks mmap_sem > task_unlock mmput atomic_dec_and_test # = 1 exit_oom_victim down_read_trylock # failed - no reclaim mmput_async # Takes unpredictable amount of time < new OOM situation > the final __mmput will be executed in the delayed context which might happen far in the future. Such a race is highly unlikely because the write holder of mmap_sem would have to be an external task (all direct holders are already killed or exiting) and it usually have to pin mm_users in order to do anything reasonable. We can, however, make sure that the mmput_async is only called when we do not back off and reap some memory. That would reduce the impact of the delayed __mmput because the real content would be already freed. Pin mm_count to keep it alive after we drop task_lock and before we try to get mmap_sem. If the mmap_sem succeeds we can try to grab mm_users reference and then go on with unmapping the address space. It is not clear whether this race is possible at all but it is better to be more robust and do not pin mm_users unless we are sure we are actually doing some real work during __oom_reap_task. Link: http://lkml.kernel.org/r/1465306987-30297-1-git-send-email-mhocko@kernel.orgSigned-off-by:
Michal Hocko <mhocko@suse.com> Reported-by:
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Chen Gang authored
Correct the function parameters alignment, since original code already use both tabs and white spaces together for the incorrect parameters alignment functions. If one line can hold one statement within 80 columns, let it in one line (original code did not consider about the tabs/spaces for 2nd line when a statement is separated into 2 lines). Try to let '' aligned within one macro, since all related lines are short enough. Remove useless statement "idx = 0;", and always assign rgn within the 'for' statement. Link: http://lkml.kernel.org/r/1464904899-1714-1-git-send-email-chengang@emindsoft.com.cnSigned-off-by:
Chen Gang <gang.chen.5i5j@gmail.com> Signed-off-by:
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Minchan Kim authored
zram is very popular for some of the embedded world (e.g., TV, mobile phones). On those system, zsmalloc's consumed memory size is never trivial (one of example from real product system, total memory: 800M, zsmalloc consumed: 150M), so we have used this out of tree patch to monitor system memory behavior via /proc/vmstat. With zsmalloc in vmstat, it helps in tracking down system behavior due to memory usage. [minchan@kernel.org: zsmalloc: follow up zsmalloc vmstat] Link: http://lkml.kernel.org/r/20160607091737.GC23435@bbox [akpm@linux-foundation.org: fix build with CONFIG_ZSMALLOC=m] Link: http://lkml.kernel.org/r/1464919731-13255-1-git-send-email-minchan@kernel.orgSigned-off-by:
Minchan Kim <minchan@kernel.org> Cc: Sangseok Lee <sangseok.lee@lge.com> Cc: Chanho Min <chanho.min@lge.com> Cc: Chan Gyun Jeong <chan.jeong@lge.com> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Signed-off-by:
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Vlastimil Babka authored
I have noticed that frontswap.h first declares "frontswap_enabled" as extern bool variable, and then overrides it with "#define frontswap_enabled (1)" for CONFIG_FRONTSWAP=Y or (0) when disabled. The bool variable isn't actually instantiated anywhere. This all looks like an unfinished attempt to make frontswap_enabled reflect whether a backend is instantiated. But in the current state, all frontswap hooks call unconditionally into frontswap.c just to check if frontswap_ops is non-NULL. This should at least be checked inline, but we can further eliminate the overhead when CONFIG_FRONTSWAP is enabled and no backend registered, using a static key that is initially disabled, and gets enabled only upon first backend registration. Thus, checks for "frontswap_enabled" are replaced with "frontswap_enabled()" wrapping the static key check. There are two exceptions: - xen's selfballoon_process() was testing frontswap_enabled in code guarded by #ifdef CONFIG_FRONTSWAP, which was effectively always true when reachable. The patch just removes this check. Using frontswap_enabled() does not sound correct here, as this can be true even without xen's own backend being registered. - in SYSCALL_DEFINE2(swapon), change the check to IS_ENABLED(CONFIG_FRONTSWAP) as it seems the bitmap allocation cannot currently be postponed until a backend is registered. This means that frontswap will still have some memory overhead by being configured, but without a backend. After the patch, we can expect that some functions in frontswap.c are called only when frontswap_ops is non-NULL. Change the checks there to VM_BUG_ONs. While at it, convert other BUG_ONs to VM_BUG_ONs as frontswap has been stable for some time. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1463152235-9717-1-git-send-email-vbabka@suse.czSigned-off-by:
Vlastimil Babka <vbabka@suse.cz> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by:
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Tetsuo Handa authored
oom_scan_process_thread() does not use totalpages argument. oom_badness() uses it. Link: http://lkml.kernel.org/r/1463796041-7889-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jpSigned-off-by:
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Vladimir Davydov authored
Unix sockets can consume a significant amount of system memory, hence they should be accounted to kmemcg. Since unix socket buffers are always allocated from process context, all we need to do to charge them to kmemcg is set __GFP_ACCOUNT in sock->sk_allocation mask. Eric asked: > 1) What happens when a buffer, allocated from socket <A> lands in a > different socket <B>, maybe owned by another user/process. > > Who owns it now, in term of kmemcg accounting ? We never move memcg charges. E.g. if two processes from different cgroups are sharing a memory region, each page will be charged to the process which touched it first. Or if two processes are working with the same directory tree, inodes and dentries will be charged to the first user. The same is fair for unix socket buffers - they will be charged to the sender. > 2) Has performance impact been evaluated ? I ran netperf STREAM_STREAM with default options in a kmemcg on a 4 core x2 HT box. The results are below: # clients bandwidth (10^6bits/sec) base patched 1 67643 +- 725 64874 +- 353 - 4.0 % 4 193585 +- 2516 186715 +- 1460 - 3.5 % 8 194820 +- 377 187443 +- 1229 - 3.7 % So the accounting doesn't come for free - it takes ~4% of performance. I believe we could optimize it by using per cpu batching not only on charge, but also on uncharge in memcg core, but that's beyond the scope of this patch set - I'll take a look at this later. Anyway, if performance impact is found to be unacceptable, it is always possible to disable kmem accounting at boot time (cgroup.memory=nokmem) or not use memory cgroups at runtime at all (thanks to jump labels there'll be no overhead even if they are compiled in). Link: http://lkml.kernel.org/r/fcfe6cae27a59fbc5e40145664b3cf085a560c68.1464079538.git.vdavydov@virtuozzo.comSigned-off-by:Vladimir Davydov <vdavydov@virtuozzo.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by:
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Vladimir Davydov authored
Pipes can consume a significant amount of system memory, hence they should be accounted to kmemcg. This patch marks pipe_inode_info and anonymous pipe buffer page allocations as __GFP_ACCOUNT so that they would be charged to kmemcg. Note, since a pipe buffer page can be "stolen" and get reused for other purposes, including mapping to userspace, we clear PageKmemcg thus resetting page->_mapcount and uncharge it in anon_pipe_buf_steal, which is introduced by this patch. A note regarding anon_pipe_buf_steal implementation. We allow to steal the page if its ref count equals 1. It looks racy, but it is correct for anonymous pipe buffer pages, because: - We lock out all other pipe users, because ->steal is called with pipe_lock held, so the page can't be spliced to another pipe from under us. - The page is not on LRU and it never was. - Thus a parallel thread can access it only by PFN. Although this is quite possible (e.g. see page_idle_get_page and balloon_page_isolate) this is not dangerous, because all such functions do is increase page ref count, check if the page is the one they are looking for, and decrease ref count if it isn't. Since our page is clean except for PageKmemcg mark, which doesn't conflict with other _mapcount users, the worst that can happen is we see page_count > 2 due to a transient ref, in which case we false-positively abort ->steal, which is still fine, because ->steal is not guaranteed to succeed. Link: http://lkml.kernel.org/r/20160527150313.GD26059@esperanzaSigned-off-by:
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Vladimir Davydov authored
Page tables can bite a relatively big chunk off system memory and their allocations are easy to trigger from userspace, so they should be accounted to kmemcg. This patch marks page table allocations as __GFP_ACCOUNT for x86. Note we must not charge allocations of kernel page tables, because they can be shared among processes from different cgroups so accounting them to a particular one can pin other cgroups for indefinitely long. So we clear __GFP_ACCOUNT flag if a page table is allocated for the kernel. Link: http://lkml.kernel.org/r/7d5c54f6a2bcbe76f03171689440003d87e6c742.1464079538.git.vdavydov@virtuozzo.comSigned-off-by:
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Vladimir Davydov authored
Page table pages are batched-freed in release_pages on most architectures. If we want to charge them to kmemcg (this is what is done later in this series), we need to teach mem_cgroup_uncharge_list to handle kmem pages. Link: http://lkml.kernel.org/r/18d5c09e97f80074ed25b97a7d0f32b95d875717.1464079538.git.vdavydov@virtuozzo.comSigned-off-by:
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Vladimir Davydov authored
Currently, to charge a non-slab allocation to kmemcg one has to use alloc_kmem_pages helper with __GFP_ACCOUNT flag. A page allocated with this helper should finally be freed using free_kmem_pages, otherwise it won't be uncharged. This API suits its current users fine, but it turns out to be impossible to use along with page reference counting, i.e. when an allocation is supposed to be freed with put_page, as it is the case with pipe or unix socket buffers. To overcome this limitation, this patch moves charging/uncharging to generic page allocator paths, i.e. to __alloc_pages_nodemask and free_pages_prepare, and zaps alloc/free_kmem_pages helpers. This way, one can use any of the available page allocation functions to get the allocated page charged to kmemcg - it's enough to pass __GFP_ACCOUNT, just like in case of kmalloc and friends. A charged page will be automatically uncharged on free. To make it possible, we need to mark pages charged to kmemcg somehow. To avoid introducing a new page flag, we make use of page->_mapcount for marking such pages. Since pages charged to kmemcg are not supposed to be mapped to userspace, it should work just fine. There are other (ab)users of page->_mapcount - buddy and balloon pages - but we don't conflict with them. In case kmemcg is compiled out or not used at runtime, this patch introduces no overhead to generic page allocator paths. If kmemcg is used, it will be plus one gfp flags check on alloc and plus one page->_mapcount check on free, which shouldn't hurt performance, because the data accessed are hot. Link: http://lkml.kernel.org/r/a9736d856f895bcb465d9f257b54efe32eda6f99.1464079538.git.vdavydov@virtuozzo.comSigned-off-by:
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Vladimir Davydov authored
- Handle memcg_kmem_enabled check out to the caller. This reduces the number of function definitions making the code easier to follow. At the same time it doesn't result in code bloat, because all of these functions are used only in one or two places. - Move __GFP_ACCOUNT check to the caller as well so that one wouldn't have to dive deep into memcg implementation to see which allocations are charged and which are not. - Refresh comments. Link: http://lkml.kernel.org/r/52882a28b542c1979fd9a033b4dc8637fc347399.1464079537.git.vdavydov@virtuozzo.comSigned-off-by:
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Vladimir Davydov authored
- Add a proper comment to page->_mapcount. - Introduce a macro for generating helper functions. - Place all special page->_mapcount values next to each other so that readers can see all possible values and so we don't get duplicates. Link: http://lkml.kernel.org/r/502f49000e0b63e6c62e338fac6b420bf34fb526.1464079537.git.vdavydov@virtuozzo.comSigned-off-by:
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Vladimir Davydov authored
This patchset implements per kmemcg accounting of page tables (x86-only), pipe buffers, and unix socket buffers. Patches 1-3 are just cleanups that are not supposed to introduce any functional changes. Patches 4 and 5 move charge/uncharge to generic page allocator paths for the sake of accounting pipe and unix socket buffers. Patches 5-7 make x86 page tables, pipe buffers, and unix socket buffers accountable. This patch (of 8): ... to reduce indentation level thus leaving more space for comments. Link: http://lkml.kernel.org/r/f34ffe70fce2b0b9220856437f77972d67c14275.1464079537.git.vdavydov@virtuozzo.comSigned-off-by:
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Aneesh Kumar K.V authored
This allows an arch which needs to do special handing with respect to different page size when flushing tlb to implement the same in mmu gather. Link: http://lkml.kernel.org/r/1465049193-22197-3-git-send-email-aneesh.kumar@linux.vnet.ibm.comSigned-off-by:
Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Hugh Dickins <hughd@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Mel Gorman <mgorman@suse.de> Cc: David Rientjes <rientjes@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan.kim@gmail.com> Signed-off-by:
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Aneesh Kumar K.V authored
This updates the generic and arch specific implementation to return true if we need to do a tlb flush. That means if a __tlb_remove_page indicate a flush is needed, the page we try to remove need to be tracked and added again after the flush. We need to track it because we have already update the pte to none and we can't just loop back. This change is done to enable us to do a tlb_flush when we try to flush a range that consists of different page sizes. For architectures like ppc64, we can do a range based tlb flush and we need to track page size for that. When we try to remove a huge page, we will force a tlb flush and starts a new mmu gather. [aneesh.kumar@linux.vnet.ibm.com: mm-change-the-interface-for-__tlb_remove_page-v3] Link: http://lkml.kernel.org/r/1465049193-22197-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com Link: http://lkml.kernel.org/r/1464860389-29019-2-git-send-email-aneesh.kumar@linux.vnet.ibm.comSigned-off-by:
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Aneesh Kumar K.V authored
For hugetlb like THP (and unlike regular page), we do tlb flush after dropping ptl. Because of the above, we don't need to track force_flush like we do now. Instead we can simply call tlb_remove_page() which will do the flush if needed. No functionality change in this patch. Link: http://lkml.kernel.org/r/1465049193-22197-1-git-send-email-aneesh.kumar@linux.vnet.ibm.comSigned-off-by:
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Naoya Horiguchi authored
split_huge_pmd() doesn't guarantee that the pmd is normal pmd pointing to pte entries, which can be checked with pmd_trans_unstable(). Some callers make this assertion and some do it differently and some not, so let's do it in a unified manner. Link: http://lkml.kernel.org/r/1464741400-12143-1-git-send-email-n-horiguchi@ah.jp.nec.comSigned-off-by:
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by:
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Joonsoo Kim authored
When there is an isolated_page, post_alloc_hook() is called with page but __free_pages() is called with isolated_page. Since they are the same so no problem but it's very confusing. To reduce it, this patch changes isolated_page to boolean type and uses page variable consistently. Link: http://lkml.kernel.org/r/1466150259-27727-10-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by:
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Joonsoo Kim authored
This patch is motivated from Hugh and Vlastimil's concern [1]. There are two ways to get freepage from the allocator. One is using normal memory allocation API and the other is __isolate_free_page() which is internally used for compaction and pageblock isolation. Later usage is rather tricky since it doesn't do whole post allocation processing done by normal API. One problematic thing I already know is that poisoned page would not be checked if it is allocated by __isolate_free_page(). Perhaps, there would be more. We could add more debug logic for allocated page in the future and this separation would cause more problem. I'd like to fix this situation at this time. Solution is simple. This patch commonize some logic for newly allocated page and uses it on all sites. This will solve the problem. [1] http://marc.info/?i=alpine.LSU.2.11.1604270029350.7066%40eggly.anvils%3E [iamjoonsoo.kim@lge.com: mm-page_alloc-introduce-post-allocation-processing-on-page-allocator-v3] Link: http://lkml.kernel.org/r/1464230275-25791-7-git-send-email-iamjoonsoo.kim@lge.com Link: http://lkml.kernel.org/r/1466150259-27727-9-git-send-email-iamjoonsoo.kim@lge.com Link: http://lkml.kernel.org/r/1464230275-25791-7-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
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Joonsoo Kim authored
Currently, we store each page's allocation stacktrace on corresponding page_ext structure and it requires a lot of memory. This causes the problem that memory tight system doesn't work well if page_owner is enabled. Moreover, even with this large memory consumption, we cannot get full stacktrace because we allocate memory at boot time and just maintain 8 stacktrace slots to balance memory consumption. We could increase it to more but it would make system unusable or change system behaviour. To solve the problem, this patch uses stackdepot to store stacktrace. It obviously provides memory saving but there is a drawback that stackdepot could fail. stackdepot allocates memory at runtime so it could fail if system has not enough memory. But, most of allocation stack are generated at very early time and there are much memory at this time. So, failure would not happen easily. And, one failure means that we miss just one page's allocation stacktrace so it would not be a big problem. In this patch, when memory allocation failure happens, we store special stracktrace handle to the page that is failed to save stacktrace. With it, user can guess memory usage properly even if failure happens. Memory saving looks as following. (4GB memory system with page_owner) (before the patch -> after the patch) static allocation: 92274688 bytes -> 25165824 bytes dynamic allocation after boot + kernel build: 0 bytes -> 327680 bytes total: 92274688 bytes -> 25493504 bytes 72% reduction in total. Note that implementation looks complex than someone would imagine because there is recursion issue. stackdepot uses page allocator and page_owner is called at page allocation. Using stackdepot in page_owner could re-call page allcator and then page_owner. That is a recursion. To detect and avoid it, whenever we obtain stacktrace, recursion is checked and page_owner is set to dummy information if found. Dummy information means that this page is allocated for page_owner feature itself (such as stackdepot) and it's understandable behavior for user. [iamjoonsoo.kim@lge.com: mm-page_owner-use-stackdepot-to-store-stacktrace-v3] Link: http://lkml.kernel.org/r/1464230275-25791-6-git-send-email-iamjoonsoo.kim@lge.com Link: http://lkml.kernel.org/r/1466150259-27727-7-git-send-email-iamjoonsoo.kim@lge.com Link: http://lkml.kernel.org/r/1464230275-25791-6-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
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Joonsoo Kim authored
Page owner will be changed to store more deep stacktrace so current temporary buffer size isn't enough. Increase it. Link: http://lkml.kernel.org/r/1464230275-25791-5-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
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Joonsoo Kim authored
split_page() calls set_page_owner() to set up page_owner to each pages. But, it has a drawback that head page and the others have different stacktrace because callsite of set_page_owner() is slightly differnt. To avoid this problem, this patch copies head page's page_owner to the others. It needs to introduce new function, split_page_owner() but it also remove the other function, get_page_owner_gfp() so looks good to do. Link: http://lkml.kernel.org/r/1464230275-25791-4-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
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Joonsoo Kim authored
Currently, copy_page_owner() doesn't copy all the owner information. It skips last_migrate_reason because copy_page_owner() is used for migration and it will be properly set soon. But, following patch will use copy_page_owner() and this skip will cause the problem that allocated page has uninitialied last_migrate_reason. To prevent it, this patch also copy last_migrate_reason in copy_page_owner(). Link: http://lkml.kernel.org/r/1464230275-25791-3-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
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Joonsoo Kim authored
It's not necessary to initialized page_owner with holding the zone lock. It would cause more contention on the zone lock although it's not a big problem since it is just debug feature. But, it is better than before so do it. This is also preparation step to use stackdepot in page owner feature. Stackdepot allocates new pages when there is no reserved space and holding the zone lock in this case will cause deadlock. Link: http://lkml.kernel.org/r/1464230275-25791-2-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
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Joonsoo Kim authored
We don't need to split freepages with holding the zone lock. It will cause more contention on zone lock so not desirable. [rientjes@google.com: if __isolate_free_page() fails, avoid adding to freelist so we don't call map_pages() with it] Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1606211447001.43430@chino.kir.corp.google.com Link: http://lkml.kernel.org/r/1464230275-25791-1-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by:
David Rientjes <rientjes@google.com> Signed-off-by:
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Minchan Kim authored
Static check warns using tag as bit shifter. It doesn't break current working but not good for redability. Let's use OBJ_TAG_BIT as bit shifter instead of OBJ_ALLOCATED_TAG. Link: http://lkml.kernel.org/r/20160607045146.GF26230@bboxSigned-off-by:
Dan Carpenter <dan.carpenter@oracle.com> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Signed-off-by:
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Minchan Kim authored
Zsmalloc is ready for page migration so zram can use __GFP_MOVABLE from now on. I did test to see how it helps to make higher order pages. Test scenario is as follows. KVM guest, 1G memory, ext4 formated zram block device, for i in `seq 1 8`; do dd if=/dev/vda1 of=mnt/test$i.txt bs=128M count=1 & done wait `pidof dd` for i in `seq 1 2 8`; do rm -rf mnt/test$i.txt done fstrim -v mnt echo "init" cat /proc/buddyinfo echo "compaction" echo 1 > /proc/sys/vm/compact_memory cat /proc/buddyinfo old: init Node 0, zone DMA 208 120 51 41 11 0 0 0 0 0 0 Node 0, zone DMA32 16380 13777 9184 3805 789 54 3 0 0 0 0 compaction Node 0, zone DMA 132 82 40 39 16 2 1 0 0 0 0 Node 0, zone DMA32 5219 5526 4969 3455 1831 677 139 15 0 0 0 new: init Node 0, zone DMA 379 115 97 19 2 0 0 0 0 0 0 Node 0, zone DMA32 18891 16774 10862 3947 637 21 0 0 0 0 0 compaction Node 0, zone DMA 214 66 87 29 10 3 0 0 0 0 0 Node 0, zone DMA32 1612 3139 3154 2469 1745 990 384 94 7 0 0 As you can see, compaction made so many high-order pages. Yay! Link: http://lkml.kernel.org/r/1464736881-24886-13-git-send-email-minchan@kernel.orgSigned-off-by:Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:
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Minchan Kim authored
This patch introduces run-time migration feature for zspage. For migration, VM uses page.lru field so it would be better to not use page.next field which is unified with page.lru for own purpose. For that, firstly, we can get first object offset of the page via runtime calculation instead of using page.index so we can use page.index as link for page chaining instead of page.next. In case of huge object, it stores handle to page.index instead of next link of page chaining because huge object doesn't need to next link for page chaining. So get_next_page need to identify huge object to return NULL. For it, this patch uses PG_owner_priv_1 flag of the page flag. For migration, it supports three functions * zs_page_isolate It isolates a zspage which includes a subpage VM want to migrate from class so anyone cannot allocate new object from the zspage. We could try to isolate a zspage by the number of subpage so subsequent isolation trial of other subpage of the zpsage shouldn't fail. For that, we introduce zspage.isolated count. With that, zs_page_isolate can know whether zspage is already isolated or not for migration so if it is isolated for migration, subsequent isolation trial can be successful without trying further isolation. * zs_page_migrate First of all, it holds write-side zspage->lock to prevent migrate other subpage in zspage. Then, lock all objects in the page VM want to migrate. The reason we should lock all objects in the page is due to race between zs_map_object and zs_page_migrate. zs_map_object zs_page_migrate pin_tag(handle) obj = handle_to_obj(handle) obj_to_location(obj, &page, &obj_idx); write_lock(&zspage->lock) if (!trypin_tag(handle)) goto unpin_object zspage = get_zspage(page); read_lock(&zspage->lock); If zs_page_migrate doesn't do trypin_tag, zs_map_object's page can be stale by migration so it goes crash. If it locks all of objects successfully, it copies content from old page to new one, finally, create new zspage chain with new page. And if it's last isolated subpage in the zspage, put the zspage back to class. * zs_page_putback It returns isolated zspage to right fullness_group list if it fails to migrate a page. If it find a zspage is ZS_EMPTY, it queues zspage freeing to workqueue. See below about async zspage freeing. This patch introduces asynchronous zspage free. The reason to need it is we need page_lock to clear PG_movable but unfortunately, zs_free path should be atomic so the apporach is try to grab page_lock. If it got page_lock of all of pages successfully, it can free zspage immediately. Otherwise, it queues free request and free zspage via workqueue in process context. If zs_free finds the zspage is isolated when it try to free zspage, it delays the freeing until zs_page_putback finds it so it will free free the zspage finally. In this patch, we expand fullness_list from ZS_EMPTY to ZS_FULL. First of all, it will use ZS_EMPTY list for delay freeing. And with adding ZS_FULL list, it makes to identify whether zspage is isolated or not via list_empty(&zspage->list) test. [minchan@kernel.org: zsmalloc: keep first object offset in struct page] Link: http://lkml.kernel.org/r/1465788015-23195-1-git-send-email-minchan@kernel.org [minchan@kernel.org: zsmalloc: zspage sanity check] Link: http://lkml.kernel.org/r/20160603010129.GC3304@bbox Link: http://lkml.kernel.org/r/1464736881-24886-12-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
Zsmalloc stores first free object's <PFN, obj_idx> position into freeobj in each zspage. If we change it with index from first_page instead of position, it makes page migration simple because we don't need to correct other entries for linked list if a page is migrated out. Link: http://lkml.kernel.org/r/1464736881-24886-11-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
Currently, putback_zspage does free zspage under class->lock if fullness become ZS_EMPTY but it makes trouble to implement locking scheme for new zspage migration. So, this patch is to separate free_zspage from putback_zspage and free zspage out of class->lock which is preparation for zspage migration. Link: http://lkml.kernel.org/r/1464736881-24886-10-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
We have squeezed meta data of zspage into first page's descriptor. So, to get meta data from subpage, we should get first page first of all. But it makes trouble to implment page migration feature of zsmalloc because any place where to get first page from subpage can be raced with first page migration. IOW, first page it got could be stale. For preventing it, I have tried several approahces but it made code complicated so finally, I concluded to separate metadata from first page. Of course, it consumes more memory. IOW, 16bytes per zspage on 32bit at the moment. It means we lost 1% at *worst case*(40B/4096B) which is not bad I think at the cost of maintenance. Link: http://lkml.kernel.org/r/1464736881-24886-9-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
For page migration, we need to create page chain of zspage dynamically so this patch factors it out from alloc_zspage. Link: http://lkml.kernel.org/r/1464736881-24886-8-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
Upcoming patch will change how to encode zspage meta so for easy review, this patch wraps code to access metadata as accessor. Link: http://lkml.kernel.org/r/1464736881-24886-7-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
Use kernel standard bit spin-lock instead of custom mess. Even, it has a bug which doesn't disable preemption. The reason we don't have any problem is that we have used it during preemption disable section by class->lock spinlock. So no need to go to stable. Link: http://lkml.kernel.org/r/1464736881-24886-6-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
Every zspage in a size_class has same number of max objects so we could move it to a size_class. Link: http://lkml.kernel.org/r/1464736881-24886-5-git-send-email-minchan@kernel.orgSigned-off-by:
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Minchan Kim authored
Now, VM has a feature to migrate non-lru movable pages so balloon doesn't need custom migration hooks in migrate.c and compaction.c. Instead, this patch implements the page->mapping->a_ops-> {isolate|migrate|putback} functions. With that, we could remove hooks for ballooning in general migration functions and make balloon compaction simple. [akpm@linux-foundation.org: compaction.h requires that the includer first include node.h] Link: http://lkml.kernel.org/r/1464736881-24886-4-git-send-email-minchan@kernel.orgSigned-off-by:Gioh Kim <gi-oh.kim@profitbricks.com> Signed-off-by:
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Minchan Kim authored
We have allowed migration for only LRU pages until now and it was enough to make high-order pages. But recently, embedded system(e.g., webOS, android) uses lots of non-movable pages(e.g., zram, GPU memory) so we have seen several reports about troubles of small high-order allocation. For fixing the problem, there were several efforts (e,g,. enhance compaction algorithm, SLUB fallback to 0-order page, reserved memory, vmalloc and so on) but if there are lots of non-movable pages in system, their solutions are void in the long run. So, this patch is to support facility to change non-movable pages with movable. For the feature, this patch introduces functions related to migration to address_space_operations as well as some page flags. If a driver want to make own pages movable, it should define three functions which are function pointers of struct address_space_operations. 1. bool (*isolate_page) (struct page *page, isolate_mode_t mode); What VM expects on isolate_page function of driver is to return *true* if driver isolates page successfully. On returing true, VM marks the page as PG_isolated so concurrent isolation in several CPUs skip the page for isolation. If a driver cannot isolate the page, it should return *false*. Once page is successfully isolated, VM uses page.lru fields so driver shouldn't expect to preserve values in that fields. 2. int (*migratepage) (struct address_space *mapping, struct page *newpage, struct page *oldpage, enum migrate_mode); After isolation, VM calls migratepage of driver with isolated page. The function of migratepage is to move content of the old page to new page and set up fields of struct page newpage. Keep in mind that you should indicate to the VM the oldpage is no longer movable via __ClearPageMovable() under page_lock if you migrated the oldpage successfully and returns 0. If driver cannot migrate the page at the moment, driver can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time because VM interprets -EAGAIN as "temporal migration failure". On returning any error except -EAGAIN, VM will give up the page migration without retrying in this time. Driver shouldn't touch page.lru field VM using in the functions. 3. void (*putback_page)(struct page *); If migration fails on isolated page, VM should return the isolated page to the driver so VM calls driver's putback_page with migration failed page. In this function, driver should put the isolated page back to the own data structure. 4. non-lru movable page flags There are two page flags for supporting non-lru movable page. * PG_movable Driver should use the below function to make page movable under page_lock. void __SetPageMovable(struct page *page, struct address_space *mapping) It needs argument of address_space for registering migration family functions which will be called by VM. Exactly speaking, PG_movable is not a real flag of struct page. Rather than, VM reuses page->mapping's lower bits to represent it. #define PAGE_MAPPING_MOVABLE 0x2 page->mapping = page->mapping | PAGE_MAPPING_MOVABLE; so driver shouldn't access page->mapping directly. Instead, driver should use page_mapping which mask off the low two bits of page->mapping so it can get right struct address_space. For testing of non-lru movable page, VM supports __PageMovable function. However, it doesn't guarantee to identify non-lru movable page because page->mapping field is unified with other variables in struct page. As well, if driver releases the page after isolation by VM, page->mapping doesn't have stable value although it has PAGE_MAPPING_MOVABLE (Look at __ClearPageMovable). But __PageMovable is cheap to catch whether page is LRU or non-lru movable once the page has been isolated. Because LRU pages never can have PAGE_MAPPING_MOVABLE in page->mapping. It is also good for just peeking to test non-lru movable pages before more expensive checking with lock_page in pfn scanning to select victim. For guaranteeing non-lru movable page, VM provides PageMovable function. Unlike __PageMovable, PageMovable functions validates page->mapping and mapping->a_ops->isolate_page under lock_page. The lock_page prevents sudden destroying of page->mapping. Driver using __SetPageMovable should clear the flag via __ClearMovablePage under page_lock before the releasing the page. * PG_isolated To prevent concurrent isolation among several CPUs, VM marks isolated page as PG_isolated under lock_page. So if a CPU encounters PG_isolated non-lru movable page, it can skip it. Driver doesn't need to manipulate the flag because VM will set/clear it automatically. Keep in mind that if driver sees PG_isolated page, it means the page have been isolated by VM so it shouldn't touch page.lru field. PG_isolated is alias with PG_reclaim flag so driver shouldn't use the flag for own purpose. [opensource.ganesh@gmail.com: mm/compaction: remove local variable is_lru] Link: http://lkml.kernel.org/r/20160618014841.GA7422@leo-test Link: http://lkml.kernel.org/r/1464736881-24886-3-git-send-email-minchan@kernel.orgSigned-off-by:
Ganesh Mahendran <opensource.ganesh@gmail.com> Acked-by:
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Minchan Kim authored
Recently, I got many reports about perfermance degradation in embedded system(Android mobile phone, webOS TV and so on) and easy fork fail. The problem was fragmentation caused by zram and GPU driver mainly. With memory pressure, their pages were spread out all of pageblock and it cannot be migrated with current compaction algorithm which supports only LRU pages. In the end, compaction cannot work well so reclaimer shrinks all of working set pages. It made system very slow and even to fail to fork easily which requires order-[2 or 3] allocations. Other pain point is that they cannot use CMA memory space so when OOM kill happens, I can see many free pages in CMA area, which is not memory efficient. In our product which has big CMA memory, it reclaims zones too exccessively to allocate GPU and zram page although there are lots of free space in CMA so system becomes very slow easily. To solve these problem, this patch tries to add facility to migrate non-lru pages via introducing new functions and page flags to help migration. struct address_space_operations { .. .. bool (*isolate_page)(struct page *, isolate_mode_t); void (*putback_page)(struct page *); .. } new page flags PG_movable PG_isolated For details, please read description in "mm: migrate: support non-lru movable page migration". Originally, Gioh Kim had tried to support this feature but he moved so I took over the work. I took many code from his work and changed a little bit and Konstantin Khlebnikov helped Gioh a lot so he should deserve to have many credit, too. And I should mention Chulmin who have tested this patchset heavily so I can find many bugs from him. :) Thanks, Gioh, Konstantin and Chulmin! This patchset consists of five parts. 1. clean up migration mm: use put_page to free page instead of putback_lru_page 2. add non-lru page migration feature mm: migrate: support non-lru movable page migration 3. rework KVM memory-ballooning mm: balloon: use general non-lru movable page feature 4. zsmalloc refactoring for preparing page migration zsmalloc: keep max_object in size_class zsmalloc: use bit_spin_lock zsmalloc: use accessor zsmalloc: factor page chain functionality out zsmalloc: introduce zspage structure zsmalloc: separate free_zspage from putback_zspage zsmalloc: use freeobj for index 5. zsmalloc page migration zsmalloc: page migration support zram: use __GFP_MOVABLE for memory allocation This patch (of 12): Procedure of page migration is as follows: First of all, it should isolate a page from LRU and try to migrate the page. If it is successful, it releases the page for freeing. Otherwise, it should put the page back to LRU list. For LRU pages, we have used putback_lru_page for both freeing and putback to LRU list. It's okay because put_page is aware of LRU list so if it releases last refcount of the page, it removes the page from LRU list. However, It makes unnecessary operations (e.g., lru_cache_add, pagevec and flags operations. It would be not significant but no worth to do) and harder to support new non-lru page migration because put_page isn't aware of non-lru page's data structure. To solve the problem, we can add new hook in put_page with PageMovable flags check but it can increase overhead in hot path and needs new locking scheme to stabilize the flag check with put_page. So, this patch cleans it up to divide two semantic(ie, put and putback). If migration is successful, use put_page instead of putback_lru_page and use putback_lru_page only on failure. That makes code more readable and doesn't add overhead in put_page. Comment from Vlastimil "Yeah, and compaction (perhaps also other migration users) has to drain the lru pvec... Getting rid of this stuff is worth even by itself." Link: http://lkml.kernel.org/r/1464736881-24886-2-git-send-email-minchan@kernel.orgSigned-off-by: -
Sergey Senozhatsky authored
We now allocate streams from CPU_UP hot-plug path, there are no context-dependent stream allocations anymore and we can schedule from zcomp_strm_alloc(). Use GFP_KERNEL directly and drop a gfp_t parameter. Link: http://lkml.kernel.org/r/20160531122017.2878-9-sergey.senozhatsky@gmail.comSigned-off-by:
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Sergey Senozhatsky authored
Add "deflate", "lz4hc", "842" algorithms to the list of known compression backends. The real availability of those algorithms, however, depends on the corresponding CONFIG_CRYPTO_FOO config options. [sergey.senozhatsky@gmail.com: zram-add-more-compression-algorithms-v3] Link: http://lkml.kernel.org/r/20160604024902.11778-7-sergey.senozhatsky@gmail.com Link: http://lkml.kernel.org/r/20160531122017.2878-8-sergey.senozhatsky@gmail.comSigned-off-by:
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