- 14 Jan, 2011 40 commits
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Daisuke Nishimura authored
Commit b1dd693e ("memcg: avoid deadlock between move charge and try_charge()") can cause another deadlock about mmap_sem on task migration if cpuset and memcg are mounted onto the same mount point. After the commit, cgroup_attach_task() has sequence like: cgroup_attach_task() ss->can_attach() cpuset_can_attach() mem_cgroup_can_attach() down_read(&mmap_sem) (1) ss->attach() cpuset_attach() mpol_rebind_mm() down_write(&mmap_sem) (2) up_write(&mmap_sem) cpuset_migrate_mm() do_migrate_pages() down_read(&mmap_sem) up_read(&mmap_sem) mem_cgroup_move_task() mem_cgroup_clear_mc() up_read(&mmap_sem) We can cause deadlock at (2) because we've already aquire the mmap_sem at (1). But the commit itself is necessary to fix deadlocks which have existed before the commit like: Ex.1) move charge | try charge --------------------------------------+------------------------------ mem_cgroup_can_attach() | down_write(&mmap_sem) mc.moving_task = current | .. mem_cgroup_precharge_mc() | __mem_cgroup_try_charge() mem_cgroup_count_precharge() | prepare_to_wait() down_read(&mmap_sem) | if (mc.moving_task) -> cannot aquire the lock | -> true | schedule() | -> move charge should wake it up Ex.2) move charge | try charge --------------------------------------+------------------------------ mem_cgroup_can_attach() | mc.moving_task = current | mem_cgroup_precharge_mc() | mem_cgroup_count_precharge() | down_read(&mmap_sem) | .. | up_read(&mmap_sem) | | down_write(&mmap_sem) mem_cgroup_move_task() | .. mem_cgroup_move_charge() | __mem_cgroup_try_charge() down_read(&mmap_sem) | prepare_to_wait() -> cannot aquire the lock | if (mc.moving_task) | -> true | schedule() | -> move charge should wake it up This patch fixes all of these problems by: 1. revert the commit. 2. To fix the Ex.1, we set mc.moving_task after mem_cgroup_count_precharge() has released the mmap_sem. 3. To fix the Ex.2, we use down_read_trylock() instead of down_read() in mem_cgroup_move_charge() and, if it has failed to aquire the lock, cancel all extra charges, wake up all waiters, and retry trylock. Signed-off-by:
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reported-by:
Ben Blum <bblum@andrew.cmu.edu> Cc: Miao Xie <miaox@cn.fujitsu.com> Cc: David Rientjes <rientjes@google.com> Cc: Paul Menage <menage@google.com> Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Minchan Kim authored
Signed-off-by:
Minchan Kim <minchan.kim@gmail.com> Acked-by:
Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by:
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by:
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Johannes Weiner authored
Adding the number of swap pages to the byte limit of a memory control group makes no sense. Convert the pages to bytes before adding them. The only user of this code is the OOM killer, and the way it is used means that the error results in a higher OOM badness value. Since the cgroup limit is the same for all tasks in the cgroup, the error should have no practical impact at the moment. But let's not wait for future or changing users to trip over it. Signed-off-by:
Johannes Weiner <hannes@cmpxchg.org> Cc: Greg Thelen <gthelen@google.com> Cc: David Rientjes <rientjes@google.com> Acked-by:
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KAMEZAWA Hiroyuki authored
Introduce a new bit spin lock, PCG_MOVE_LOCK, to synchronize the page accounting and migration code. This reworks the locking scheme of _update_stat() and _move_account() by adding new lock bit PCG_MOVE_LOCK, which is always taken under IRQ disable. 1. If pages are being migrated from a memcg, then updates to that memcg page statistics are protected by grabbing PCG_MOVE_LOCK using move_lock_page_cgroup(). In an upcoming commit, memcg dirty page accounting will be updating memcg page accounting (specifically: num writeback pages) from IRQ context (softirq). Avoid a deadlocking nested spin lock attempt by disabling irq on the local processor when grabbing the PCG_MOVE_LOCK. 2. lock for update_page_stat is used only for avoiding race with move_account(). So, IRQ awareness of lock_page_cgroup() itself is not a problem. The problem is between mem_cgroup_update_page_stat() and mem_cgroup_move_account_page(). Trade-off: * Changing lock_page_cgroup() to always disable IRQ (or local_bh) has some impacts on performance and I think it's bad to disable IRQ when it's not necessary. * adding a new lock makes move_account() slower. Score is here. Performance Impact: moving a 8G anon process. Before: real 0m0.792s user 0m0.000s sys 0m0.780s After: real 0m0.854s user 0m0.000s sys 0m0.842s This score is bad but planned patches for optimization can reduce this impact. Signed-off-by:Greg Thelen <gthelen@google.com> Reviewed-by:
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Greg Thelen authored
Replace usage of the mem_cgroup_update_file_mapped() memcg statistic update routine with two new routines: * mem_cgroup_inc_page_stat() * mem_cgroup_dec_page_stat() As before, only the file_mapped statistic is managed. However, these more general interfaces allow for new statistics to be more easily added. New statistics are added with memcg dirty page accounting. Signed-off-by:
Andrea Righi <arighi@develer.com> Acked-by:
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Greg Thelen authored
Document cgroup dirty memory interfaces and statistics. [akpm@linux-foundation.org: fix use_hierarchy description] Signed-off-by:
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Greg Thelen authored
This patchset provides the ability for each cgroup to have independent dirty page limits. Limiting dirty memory is like fixing the max amount of dirty (hard to reclaim) page cache used by a cgroup. So, in case of multiple cgroup writers, they will not be able to consume more than their designated share of dirty pages and will be forced to perform write-out if they cross that limit. The patches are based on a series proposed by Andrea Righi in Mar 2010. Overview: - Add page_cgroup flags to record when pages are dirty, in writeback, or nfs unstable. - Extend mem_cgroup to record the total number of pages in each of the interesting dirty states (dirty, writeback, unstable_nfs). - Add dirty parameters similar to the system-wide /proc/sys/vm/dirty_* limits to mem_cgroup. The mem_cgroup dirty parameters are accessible via cgroupfs control files. - Consider both system and per-memcg dirty limits in page writeback when deciding to queue background writeback or block for foreground writeback. Known shortcomings: - When a cgroup dirty limit is exceeded, then bdi writeback is employed to writeback dirty inodes. Bdi writeback considers inodes from any cgroup, not just inodes contributing dirty pages to the cgroup exceeding its limit. - When memory.use_hierarchy is set, then dirty limits are disabled. This is a implementation detail. An enhanced implementation is needed to check the chain of parents to ensure that no dirty limit is exceeded. Performance data: - A page fault microbenchmark workload was used to measure performance, which can be called in read or write mode: f = open(foo. $cpu) truncate(f, 4096) alarm(60) while (1) { p = mmap(f, 4096) if (write) *p = 1 else x = *p munmap(p) } - The workload was called for several points in the patch series in different modes: - s_read is a single threaded reader - s_write is a single threaded writer - p_read is a 16 thread reader, each operating on a different file - p_write is a 16 thread writer, each operating on a different file - Measurements were collected on a 16 core non-numa system using "perf stat --repeat 3". The -a option was used for parallel (p_*) runs. - All numbers are page fault rate (M/sec). Higher is better. - To compare the performance of a kernel without non-memcg compare the first and last rows, neither has memcg configured. The first row does not include any of these memcg patches. - To compare the performance of using memcg dirty limits, compare the baseline (2nd row titled "w/ memcg") with the the code and memcg enabled (2nd to last row titled "all patches"). root_cgroup child_cgroup s_read s_write p_read p_write s_read s_write p_read p_write mmotm w/o memcg 0.428 0.390 0.429 0.388 mmotm w/ memcg 0.411 0.378 0.391 0.362 0.412 0.377 0.385 0.363 all patches 0.384 0.360 0.370 0.348 0.381 0.363 0.368 0.347 all patches 0.431 0.402 0.427 0.395 w/o memcg This patch: Add additional flags to page_cgroup to track dirty pages within a mem_cgroup. Signed-off-by: -
Shaohua Li authored
The zone->lru_lock is heavily contented in workload where activate_page() is frequently used. We could do batch activate_page() to reduce the lock contention. The batched pages will be added into zone list when the pool is full or page reclaim is trying to drain them. For example, in a 4 socket 64 CPU system, create a sparse file and 64 processes, processes shared map to the file. Each process read access the whole file and then exit. The process exit will do unmap_vmas() and cause a lot of activate_page() call. In such workload, we saw about 58% total time reduction with below patch. Other workloads with a lot of activate_page also benefits a lot too. I tested some microbenchmarks: case-anon-cow-rand-mt 0.58% case-anon-cow-rand -3.30% case-anon-cow-seq-mt -0.51% case-anon-cow-seq -5.68% case-anon-r-rand-mt 0.23% case-anon-r-rand 0.81% case-anon-r-seq-mt -0.71% case-anon-r-seq -1.99% case-anon-rx-rand-mt 2.11% case-anon-rx-seq-mt 3.46% case-anon-w-rand-mt -0.03% case-anon-w-rand -0.50% case-anon-w-seq-mt -1.08% case-anon-w-seq -0.12% case-anon-wx-rand-mt -5.02% case-anon-wx-seq-mt -1.43% case-fork 1.65% case-fork-sleep -0.07% case-fork-withmem 1.39% case-hugetlb -0.59% case-lru-file-mmap-read-mt -0.54% case-lru-file-mmap-read 0.61% case-lru-file-mmap-read-rand -2.24% case-lru-file-readonce -0.64% case-lru-file-readtwice -11.69% case-lru-memcg -1.35% case-mmap-pread-rand-mt 1.88% case-mmap-pread-rand -15.26% case-mmap-pread-seq-mt 0.89% case-mmap-pread-seq -69.72% case-mmap-xread-rand-mt 0.71% case-mmap-xread-seq-mt 0.38% The most significent are: case-lru-file-readtwice -11.69% case-mmap-pread-rand -15.26% case-mmap-pread-seq -69.72% which use activate_page a lot. others are basically variations because each run has slightly difference. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by:
Shaohua Li <shaohua.li@intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by:
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Shaohua Li authored
Clean up code and remove duplicate code. Next patch will use pagevec_lru_move_fn introduced here too. Signed-off-by:
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Andrew Morton authored
It's old-fashioned and unneeded. akpm:/usr/src/25> size mm/page_alloc.o text data bss dec hex filename 39884 1241317 18808 1300009 13d629 mm/page_alloc.o (before) 39838 1241317 18808 1299963 13d5fb mm/page_alloc.o (after) Acked-by:
David Rientjes <rientjes@google.com> Acked-by:
Mel Gorman <mel@csn.ul.ie> Cc: Hugh Dickins <hughd@google.com> Signed-off-by:
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Hugh Dickins authored
2.6.37 added an unmap_and_move_huge_page() for memory failure recovery, but its anon_vma handling was still based around the 2.6.35 conventions. Update it to use page_lock_anon_vma, get_anon_vma, page_unlock_anon_vma, drop_anon_vma in the same way as we're now changing unmap_and_move(). I don't particularly like to propose this for stable when I've not seen its problems in practice nor tested the solution: but it's clearly out of synch at present. Signed-off-by:
Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: <stable@kernel.org> [2.6.37, 2.6.36] Signed-off-by:
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Hugh Dickins authored
Increased usage of page migration in mmotm reveals that the anon_vma locking in unmap_and_move() has been deficient since 2.6.36 (or even earlier). Review at the time of f1819427 ("mm: fix hang on anon_vma->root->lock") missed the issue here: the anon_vma to which we get a reference may already have been freed back to its slab (it is in use when we check page_mapped, but that can change), and so its anon_vma->root may be switched at any moment by reuse in anon_vma_prepare. Perhaps we could fix that with a get_anon_vma_unless_zero(), but let's not: just rely on page_lock_anon_vma() to do all the hard thinking for us, then we don't need any rcu read locking over here. In removing the rcu_unlock label: since PageAnon is a bit in page->mapping, it's impossible for a !page->mapping page to be anon; but insert VM_BUG_ON in case the implementation ever changes. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by:
Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: <stable@kernel.org> [2.6.37, 2.6.36] Signed-off-by:
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Hugh Dickins authored
It was hard to explain the page counts which were causing new LTP tests of KSM to fail: we need to drain the per-cpu pagevecs to LRU occasionally. Signed-off-by:
CAI Qian <caiqian@redhat.com> Cc:Andrea Arcangeli <aarcange@redhat.com> Signed-off-by:
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Eric B Munson authored
When parsing changes to the huge page pool sizes made from userspace via the sysfs interface, bogus input values are being covered up by nr_hugepages_store_common and nr_overcommit_hugepages_store returning 0 when strict_strtoul returns an error. This can cause an infinite loop in the nr_hugepages_store code. This patch changes the return value for these functions to -EINVAL when strict_strtoul returns an error. Signed-off-by:
Eric B Munson <emunson@mgebm.net> Reported-by:
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Eric B Munson authored
Huge pages with order >= MAX_ORDER must be allocated at boot via the kernel command line, they cannot be allocated or freed once the kernel is up and running. Currently we allow values to be written to the sysfs and sysctl files controling pool size for these huge page sizes. This patch makes the store functions for nr_hugepages and nr_overcommit_hugepages return -EINVAL when the pool for a page size >= MAX_ORDER is changed. [akpm@linux-foundation.org: avoid multiple return paths in nr_hugepages_store_common()] [caiqian@redhat.com: add checking in hugetlb_overcommit_handler()] Signed-off-by:
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Michal Hocko authored
proc_doulongvec_minmax may fail if the given buffer doesn't represent a valid number. If we provide something invalid we will initialize the resulting value (nr_overcommit_huge_pages in this case) to a random value from the stack. The issue was introduced by a3d0c6aa when the default handler has been replaced by the helper function where we do not check the return value. Reproducer: echo "" > /proc/sys/vm/nr_overcommit_hugepages [akpm@linux-foundation.org: correctly propagate proc_doulongvec_minmax return code] Signed-off-by:
Michal Hocko <mhocko@suse.cz> Cc: CAI Qian <caiqian@redhat.com> Cc: Nishanth Aravamudan <nacc@us.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by:
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Stefan Hajnoczi authored
The sync_inodes_sb() function does not have a return value. Remove the outdated documentation comment. Signed-off-by:
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by:
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Andrew Morton authored
As it stands this code will degenerate into a busy-wait if the calling task has signal_pending(). Cc: Rolf Eike Beer <eike-kernel@sf-tec.de> Signed-off-by:
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Rolf Eike Beer authored
dma_pool_free() scans for the page to free in the pool list holding the pool lock. Then it releases the lock basically to acquire it immediately again. Modify the code to only take the lock once. This will do some additional loops and computations with the lock held in if memory debugging is activated. If it is not activated the only new operations with this lock is one if and one substraction. Signed-off-by:
Rolf Eike Beer <eike-kernel@sf-tec.de> Signed-off-by:
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KyongHo Cho authored
The previous approach of calucation of combined index was page_idx & ~(1 << order)) but we have same result with page_idx & buddy_idx This reduces instructions slightly as well as enhances readability. [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix used-unintialised warning] Signed-off-by:
KyongHo Cho <pullip.cho@samsung.com> Signed-off-by:
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Jiri Kosina authored
Even if CONFIG_COMPAT_BRK is set in the kernel configuration, it can still be overriden by randomize_va_space sysctl. If this is the case, the min_brk computation in sys_brk() implementation is wrong, as it solely takes into account COMPAT_BRK setting, assuming that brk start is not randomized. But that might not be the case if randomize_va_space sysctl has been set to '2' at the time the binary has been loaded from disk. In such case, the check has to be done in a same way as in !CONFIG_COMPAT_BRK case. In addition to that, the check for the COMPAT_BRK case introduced back in a5b4592c ("brk: make sys_brk() honor COMPAT_BRK when computing lower bound") is slightly wrong -- the lower bound shouldn't be mm->end_code, but mm->end_data instead, as that's where the legacy applications expect brk section to start (i.e. immediately after last global variable). [akpm@linux-foundation.org: fix comment] Signed-off-by:
Jiri Kosina <jkosina@suse.cz> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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Jesper Juhl authored
The NODEMASK_ALLOC macro may dynamically allocate memory for its second argument ('nodes_allowed' in this context). In nr_hugepages_store_common() we may abort early if strict_strtoul() fails, but in that case we do not free the memory already allocated to 'nodes_allowed', causing a memory leak. This patch closes the leak by freeing the memory in the error path. [akpm@linux-foundation.org: use NODEMASK_FREE, per Minchan Kim] Signed-off-by:Jesper Juhl <jj@chaosbits.net> Cc: Minchan Kim <minchan.kim@gmail.com> Signed-off-by:
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Mel Gorman authored
mm: migration: use rcu_dereference_protected when dereferencing the radix tree slot during file page migration migrate_pages() -> unmap_and_move() only calls rcu_read_lock() for anonymous pages, as introduced by git commit 989f89c5 ("fix rcu_read_lock() in page migraton"). The point of the RCU protection there is part of getting a stable reference to anon_vma and is only held for anon pages as file pages are locked which is sufficient protection against freeing. However, while a file page's mapping is being migrated, the radix tree is double checked to ensure it is the expected page. This uses radix_tree_deref_slot() -> rcu_dereference() without the RCU lock held triggering the following warning. [ 173.674290] =================================================== [ 173.676016] [ INFO: suspicious rcu_dereference_check() usage. ] [ 173.676016] --------------------------------------------------- [ 173.676016] include/linux/radix-tree.h:145 invoked rcu_dereference_check() without protection! [ 173.676016] [ 173.676016] other info that might help us debug this: [ 173.676016] [ 173.676016] [ 173.676016] rcu_scheduler_active = 1, debug_locks = 0 [ 173.676016] 1 lock held by hugeadm/2899: [ 173.676016] #0: (&(&inode->i_data.tree_lock)->rlock){..-.-.}, at: [<c10e3d2b>] migrate_page_move_mapping+0x40/0x1ab [ 173.676016] [ 173.676016] stack backtrace: [ 173.676016] Pid: 2899, comm: hugeadm Not tainted 2.6.37-rc5-autobuild [ 173.676016] Call Trace: [ 173.676016] [<c128cc01>] ? printk+0x14/0x1b [ 173.676016] [<c1063502>] lockdep_rcu_dereference+0x7d/0x86 [ 173.676016] [<c10e3db5>] migrate_page_move_mapping+0xca/0x1ab [ 173.676016] [<c10e41ad>] migrate_page+0x23/0x39 [ 173.676016] [<c10e491b>] buffer_migrate_page+0x22/0x107 [ 173.676016] [<c10e48f9>] ? buffer_migrate_page+0x0/0x107 [ 173.676016] [<c10e425d>] move_to_new_page+0x9a/0x1ae [ 173.676016] [<c10e47e6>] migrate_pages+0x1e7/0x2fa This patch introduces radix_tree_deref_slot_protected() which calls rcu_dereference_protected(). Users of it must pass in the mapping->tree_lock that is protecting this dereference. Holding the tree lock protects against parallel updaters of the radix tree meaning that rcu_dereference_protected is allowable. [akpm@linux-foundation.org: remove unneeded casts] Signed-off-by:
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Andrea Arcangeli authored
Cleanup some code with common compound_trans_head helper. Signed-off-by:
Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Avi Kivity <avi@redhat.com> Signed-off-by:
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Andrea Arcangeli authored
This makes KSM full operational with THP pages. Subpages are scanned while the hugepage is still in place and delivering max cpu performance, and only if there's a match and we're going to deduplicate memory, the single hugepages with the subpage match is split. There will be no false sharing between ksmd and khugepaged. khugepaged won't collapse 2m virtual regions with KSM pages inside. ksmd also should only split pages when the checksum matches and we're likely to split an hugepage for some long living ksm page (usual ksm heuristic to avoid sharing pages that get de-cowed). Signed-off-by:
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Andrea Arcangeli authored
MADV_HUGEPAGE and MADV_NOHUGEPAGE were fully effective only if run after mmap and before touching the memory. While this is enough for most usages, it's little effort to make madvise more dynamic at runtime on an existing mapping by making khugepaged aware about madvise. MADV_HUGEPAGE: register in khugepaged immediately without waiting a page fault (that may not ever happen if all pages are already mapped and the "enabled" knob was set to madvise during the initial page faults). MADV_NOHUGEPAGE: skip vmas marked VM_NOHUGEPAGE in khugepaged to stop collapsing pages where not needed. [akpm@linux-foundation.org: tweak comment] Signed-off-by:
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Andrea Arcangeli authored
Add madvise MADV_NOHUGEPAGE to mark regions that are not important to be hugepage backed. Return -EINVAL if the vma is not of an anonymous type, or the feature isn't built into the kernel. Never silently return success. Signed-off-by:
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Andrea Arcangeli authored
Define MADV_NOHUGEPAGE. Signed-off-by:
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Andrea Arcangeli authored
Read compound_trans_order safe. Noop for CONFIG_TRANSPARENT_HUGEPAGE=n. Signed-off-by:
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Andrea Arcangeli authored
hugetlbfs was changed to allow memory failure to migrate the hugetlbfs pages and that broke THP as split_huge_page was then called on hugetlbfs pages too. compound_head/order was also run unsafe on THP pages that can be splitted at any time. All compound_head() invocations in memory-failure.c that are run on pages that aren't pinned and that can be freed and reused from under us (while compound_head is running) are buggy because compound_head can return a dangling pointer, but I'm not fixing this as this is a generic memory-failure bug not specific to THP but it applies to hugetlbfs too, so I can fix it later after THP is merged upstream. Signed-off-by:
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Andrea Arcangeli authored
Add debug checks for invariants that if broken could lead to mapcount vs page_mapcount debug checks to trigger later in split_huge_page. Signed-off-by:
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David Rientjes authored
Add hugepage statistics to per-node sysfs meminfo Reviewed-by:
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Rik van Riel authored
Make sure we scale up nr_rotated when we encounter a referenced transparent huge page. This ensures pageout scanning balance is not distorted when there are huge pages on the LRU. Signed-off-by:
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Rik van Riel authored
Count each transparent hugepage as HPAGE_PMD_NR pages in the LRU statistics, so the Active(anon) and Inactive(anon) statistics in /proc/meminfo are correct. Signed-off-by:
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Rik van Riel authored
On small systems, the extra memory used by the anti-fragmentation memory reserve and simply because huge pages are smaller than large pages can easily outweigh the benefits of less TLB misses. A less obvious concern is if run on a NUMA machine with asymmetric node sizes and one of them is very small. The reserve could make the node unusable. In case of the crashdump kernel, OOMs have been observed due to the anti-fragmentation memory reserve taking up a large fraction of the crashdump image. This patch disables transparent hugepages on systems with less than 1GB of RAM, but the hugepage subsystem is fully initialized so administrators can enable THP through /sys if desired. Signed-off-by:
Avi Kiviti <avi@redhat.com> Signed-off-by:
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Andrea Arcangeli authored
It makes no sense not to enable compaction for small order pages as we don't want to end up with bad order 2 allocations and good and graceful order 9 allocations. Signed-off-by:
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Andrea Arcangeli authored
This takes advantage of memory compaction to properly generate pages of order > 0 if regular page reclaim fails and priority level becomes more severe and we don't reach the proper watermarks. Signed-off-by:
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Andrea Arcangeli authored
It's unclear why schedule friendly kernel threads can't be taken away by the CPU through the scheduler itself. It's safer to stop them as they can trigger memory allocation, if kswapd also freezes itself to avoid generating I/O they have too. Signed-off-by:
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Andrea Arcangeli authored
For GRU and EPT, we need gup-fast to set referenced bit too (this is why it's correct to return 0 when shadow_access_mask is zero, it requires gup-fast to set the referenced bit). qemu-kvm access already sets the young bit in the pte if it isn't zero-copy, if it's zero copy or a shadow paging EPT minor fault we relay on gup-fast to signal the page is in use... We also need to check the young bits on the secondary pagetables for NPT and not nested shadow mmu as the data may never get accessed again by the primary pte. Without this closer accuracy, we'd have to remove the heuristic that avoids collapsing hugepages in hugepage virtual regions that have not even a single subpage in use. ->test_young is full backwards compatible with GRU and other usages that don't have young bits in pagetables set by the hardware and that should nuke the secondary mmu mappings when ->clear_flush_young runs just like EPT does. Removing the heuristic that checks the young bit in khugepaged/collapse_huge_page completely isn't so bad either probably but I thought it was worth it and this makes it reliable. Signed-off-by:
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Andrea Arcangeli authored
Archs implementing Transparent Hugepage Support must implement a function called has_transparent_hugepage to be sure the virtual or physical CPU supports Transparent Hugepages. Signed-off-by:
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