- 29 Apr, 2013 40 commits
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Michal Hocko authored
mem_cgroup_iter curently relies on css->id when walking down a group hierarchy tree. This is really awkward because the tree walk depends on the groups creation ordering. The only guarantee is that a parent node is visited before its children. Example: 1) mkdir -p a a/d a/b/c 2) mkdir -a a/b/c a/d Will create the same trees but the tree walks will be different: 1) a, d, b, c 2) a, b, c, d Commit 574bd9f7 ("cgroup: implement generic child / descendant walk macros") has introduced generic cgroup tree walkers which provide either pre-order or post-order tree walk. This patch converts css->id based iteration to pre-order tree walk to keep the semantic with the original iterator where parent is always visited before its subtree. cgroup_for_each_descendant_pre suggests using post_create and pre_destroy for proper synchronization with groups addidition resp. removal. This implementation doesn't use those because a new memory cgroup is initialized sufficiently for iteration in mem_cgroup_css_alloc already and css reference counting enforces that the group is alive for both the last seen cgroup and the found one resp. it signals that the group is dead and it should be skipped. If the reclaim cookie is used we need to store the last visited group into the iterator so we have to be careful that it doesn't disappear in the mean time. Elevated reference count on the css keeps it alive even though the group have been removed (parked waiting for the last dput so that it can be freed). Per node-zone-prio iter_lock has been introduced to ensure that css_tryget and iter->last_visited is set atomically. Otherwise two racing walkers could both take a references and only one release it leading to a css leak (which pins cgroup dentry). Signed-off-by:
Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Ying Han <yinghan@google.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> 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
The patchset tries to make mem_cgroup_iter saner in the way how it walks hierarchies. css->id based traversal is far from being ideal as it is not deterministic because it depends on the creation ordering. Additional to that css_id is considered a burden for cgroup maintainers because it is quite some code and memcg is the last user of it. After this series only the swap accounting uses css_id but that one will follow up later. Diffstat (if we exclude removed/added comments) looks quite promising. We got rid of some code: $ git diff mmotm... | grep -v "^[+-][[:space:]]*[/ ]\*" | diffstat b/include/linux/cgroup.h | 3 --- kernel/cgroup.c | 33 --------------------------------- mm/memcontrol.c | 4 +++- 3 files changed, 3 insertions(+), 37 deletions(-) The first patch is just preparatory and it changes when we release css of the previously returned memcg. Nothing controlversial. The second patch is the core of the patchset and it replaces css_get_next based on css_id by the generic cgroup pre-order. This brings some chalanges for the last visited group caching during the reclaim (mem_cgroup_per_zone::reclaim_iter). We have to use memcg pointers directly now which means that we have to keep a reference to those groups' css to keep them alive. I also folded iter_lock introduced by https://lkml.org/lkml/2013/1/3/295 in the previous version into this patch. Johannes felt the race I was describing should be mostly harmless and I haven't been able to trigger it so the lock doesn't deserve its own patch. It is still needed temporarily, though, because the reference counting on iter->last_visited depends on it. It will go away with the next patch. The next patch fixups an unbounded cgroup removal holdoff caused by the elevated css refcount. The issue has been observed by Ying Han. Johannes wasn't impressed by the previous version of the fix (https://lkml.org/lkml/2013/2/8/379) which cleaned up pending references during mem_cgroup_css_offline when a group is removed. He has suggested a different way when the iterator checks whether a cached memcg is still valid or no. More on that in the patch but the basic idea is that every memcg tracks the number removed subgroups and iterator records this number when a group is cached. These numbers are checked before iter->last_visited is about to be used and the iteration is restarted if it is invalid. The fourth and fifth patches are an attempt for simplification of the mem_cgroup_iter. css juggling is removed and the iteration logic is moved to a helper so that the reference counting and iteration are separated. The last patch just removes css_get_next as there is no user for it any longer. My testing looked as follows: A (use_hierarchy=1, limit_in_bytes=150M) /|\ 1 2 3 Children groups were created so that the number is never higher than 3 and their limits were random between 50-100M. Each group hosts a kernel build (starting with tar -xf so the tree is not shared and make -jNUM_CPUs/3) and terminated after random time - up to 5 minutes) and then it is removed. This should exercise both leaf and hierarchical reclaim as well as races with cgroup removals and debugging messages I added on top proved that. 100 groups were created during the test. This patch: css reference counting keeps the cgroup alive even though it has been already removed. mem_cgroup_iter relies on this fact and takes a reference to the returned group. The reference is then released on the next iteration or mem_cgroup_iter_break. mem_cgroup_iter currently releases the reference right after it gets the last css_id. This is correct because neither prev's memcg nor cgroup are accessed after then. This will change in the next patch so we need to hold the group alive a bit longer so let's move the css_put at the end of the function. Signed-off-by:
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Ying Han <yinghan@google.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
Jiang Liu <jiang.liu@huawei.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Cong Wang <amwang@redhat.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Attilio Rao <attilio.rao@citrix.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by:
Pekka Enberg <penberg@kernel.org> Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
Sam Ravnborg <sam@ravnborg.org> Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Also fix a bug that totalhigh_pages should be increased when freeing a highmem page into the buddy system. Signed-off-by:
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Jiang Liu authored
Use helper function free_highmem_page() to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
The original goal of this patchset is to fix the bug reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501 Now it has also been expanded to reduce common code used by memory initializion. This is the second part, which applies to the previous part at: http://marc.info/?l=linux-mm&m=136289696323825&w=2 It introduces a helper function free_highmem_page() to free highmem pages into the buddy system when initializing mm subsystem. Introduction of free_highmem_page() is one step forward to clean up accesses and modificaitons of totalhigh_pages, totalram_pages and zone->managed_pages etc. I hope we could remove all references to totalhigh_pages from the arch/ subdirectory. We have only tested these patchset on x86 platforms, and have done basic compliation tests using cross-compilers from ftp.kernel.org. That means some code may not pass compilation on some architectures. So any help to test this patchset are welcomed! There are several other parts still under development: Part3: refine code to manage totalram_pages, totalhigh_pages and zone->managed_pages Part4: introduce helper functions to simplify mem_init() and remove the global variable num_physpages. This patch: Introduce helper function free_highmem_page(), which will be used by architectures with HIGHMEM enabled to free highmem pages into the buddy system. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
Vineet Gupta <vgupta@synopsys.com> Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
Paul Mundt <lethal@linux-sh.org> Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Also include <asm/sections.h> to avoid local declarations. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Also include <asm/sections.h> to avoid local declarations. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Also include <asm/sections.h> to avoid local declaration. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
Hans-Christian Egtvedt <egtvedt@samfundet.no> Cc: Haavard Skinnemoen <hskinnemoen@gmail.com> Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Signed-off-by:
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Jiang Liu authored
Use common help functions to free reserved pages. Also include <asm/sections.h> to avoid local declarations. Signed-off-by:
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Jiang Liu authored
The original goal of this patchset is to fix the bug reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501 Now it has also been expanded to reduce common code used by memory initializion. This is the first part, which applies to v3.9-rc1. It introduces following common helper functions to simplify free_initmem() and free_initrd_mem() on different architectures: adjust_managed_page_count(): will be used to adjust totalram_pages, totalhigh_pages, zone->managed_pages when reserving/unresering a page. __free_reserved_page(): free a reserved page into the buddy system without adjusting page statistics info free_reserved_page(): free a reserved page into the buddy system and adjust page statistics info mark_page_reserved(): mark a page as reserved and adjust page statistics info free_reserved_area(): free a continous ranges of pages by calling free_reserved_page() free_initmem_default(): default method to free __init pages. We have only tested these patchset on x86 platforms, and have done basic compliation tests using cross-compilers from ftp.kernel.org. That means some code may not pass compilation on some architectures. So any help to test this patchset are welcomed! There are several other parts still under development: Part2: introduce free_highmem_page() to simplify freeing highmem pages Part3: refine code to manage totalram_pages, totalhigh_pages and zone->managed_pages Part4: introduce helper functions to simplify mem_init() and remove the global variable num_physpages. This patch: Code to deal with reserved/managed pages are duplicated by many architectures, so introduce common help functions to reduce duplicated code. These common help functions will also be used to concentrate code to modify totalram_pages and zone->managed_pages, which makes the code much more clear. Signed-off-by:
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