Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | [RFC][PATCH v2 6/8] wipe_page_reference return SWAP_AGAIN if VM pressulre is low and lock contention is detected. | Date | Thu, 10 Dec 2009 16:33:31 +0900 (JST) |
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Larry Woodman reported AIM7 makes serious ptelock and anon_vma_lock contention on current VM. because SplitLRU VM (since 2.6.28) remove calc_reclaim_mapped() test, then shrink_active_list() always call page_referenced() against mapped page although VM pressure is low. Lightweight VM pressure is very common situation and it easily makes ptelock contention with page fault. then, anon_vma_lock is holding long time and it makes another lock contention. then, fork/exit throughput decrease a lot.
While running workloads that do lots of forking processes, exiting processes and page reclamation(AIM 7) on large systems very high system time(100%) and lots of lock contention was observed.
CPU5: [<ffffffff814afb48>] ? _spin_lock+0x27/0x48 [<ffffffff81101deb>] ? anon_vma_link+0x2a/0x5a [<ffffffff8105d3d8>] ? dup_mm+0x242/0x40c [<ffffffff8105e0a9>] ? copy_process+0xab1/0x12be [<ffffffff8105ea07>] ? do_fork+0x151/0x330 [<ffffffff81058407>] ? default_wake_function+0x0/0x36 [<ffffffff814b0243>] ? _spin_lock_irqsave+0x2f/0x68 [<ffffffff810121d3>] ? stub_clone+0x13/0x20 [<ffffffff81011e02>] ? system_call_fastpath+0x16/0x1b
CPU4: [<ffffffff814afb4a>] ? _spin_lock+0x29/0x48 [<ffffffff81103062>] ? anon_vma_unlink+0x2a/0x84 [<ffffffff810fbab7>] ? free_pgtables+0x3c/0xe1 [<ffffffff810fd8b1>] ? exit_mmap+0xc5/0x110 [<ffffffff8105ce4c>] ? mmput+0x55/0xd9 [<ffffffff81061afd>] ? exit_mm+0x109/0x129 [<ffffffff81063846>] ? do_exit+0x1d7/0x712 [<ffffffff814b0243>] ? _spin_lock_irqsave+0x2f/0x68 [<ffffffff81063e07>] ? do_group_exit+0x86/0xb2 [<ffffffff81063e55>] ? sys_exit_group+0x22/0x3e [<ffffffff81011e02>] ? system_call_fastpath+0x16/0x1b
CPU0: [<ffffffff814afb4a>] ? _spin_lock+0x29/0x48 [<ffffffff81101ad1>] ? page_check_address+0x9e/0x16f [<ffffffff81101cb8>] ? page_referenced_one+0x53/0x10b [<ffffffff81102f5a>] ? page_referenced+0xcd/0x167 [<ffffffff810eb32d>] ? shrink_active_list+0x1ed/0x2a3 [<ffffffff810ebde9>] ? shrink_zone+0xa06/0xa38 [<ffffffff8108440a>] ? getnstimeofday+0x64/0xce [<ffffffff810ecaf9>] ? do_try_to_free_pages+0x1e5/0x362 [<ffffffff810ecd9f>] ? try_to_free_pages+0x7a/0x94 [<ffffffff810ea66f>] ? isolate_pages_global+0x0/0x242 [<ffffffff810e57b9>] ? __alloc_pages_nodemask+0x397/0x572 [<ffffffff810e3c1e>] ? __get_free_pages+0x19/0x6e [<ffffffff8105d6c9>] ? copy_process+0xd1/0x12be [<ffffffff81204eb2>] ? avc_has_perm+0x5c/0x84 [<ffffffff81130db8>] ? user_path_at+0x65/0xa3 [<ffffffff8105ea07>] ? do_fork+0x151/0x330 [<ffffffff810b7935>] ? check_for_new_grace_period+0x78/0xab [<ffffffff810121d3>] ? stub_clone+0x13/0x20 [<ffffffff81011e02>] ? system_call_fastpath+0x16/0x1b
------------------------------------------------------------------------------ PerfTop: 864 irqs/sec kernel:99.7% [100000 cycles], (all, 8 CPUs) ------------------------------------------------------------------------------
samples pcnt RIP kernel function ______ _______ _____ ________________ _______________
3235.00 - 75.1% - ffffffff814afb21 : _spin_lock 670.00 - 15.6% - ffffffff81101a33 : page_check_address 165.00 - 3.8% - ffffffffa01cbc39 : rpc_sleep_on [sunrpc] 40.00 - 0.9% - ffffffff81102113 : try_to_unmap_one 29.00 - 0.7% - ffffffff81101c65 : page_referenced_one 27.00 - 0.6% - ffffffff81101964 : vma_address 8.00 - 0.2% - ffffffff8125a5a0 : clear_page_c 6.00 - 0.1% - ffffffff8125a5f0 : copy_page_c 6.00 - 0.1% - ffffffff811023ca : try_to_unmap_anon 5.00 - 0.1% - ffffffff810fb014 : copy_page_range 5.00 - 0.1% - ffffffff810e4d18 : get_page_from_freelist
Then, We use trylock for avoiding ptelock contention if VM pressure is low.
Reported-by: Larry Woodman <lwoodman@redhat.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Rik van Riel <riel@redhat.com> --- include/linux/rmap.h | 4 ++++ mm/rmap.c | 16 ++++++++++++---- mm/vmscan.c | 1 + 3 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 564d981..499972e 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -110,6 +110,10 @@ static inline void page_dup_rmap(struct page *page) struct page_reference_context { int is_page_locked; + + /* if 1, we might give up to wipe when find lock contention. */ + int soft_try; + unsigned long referenced; unsigned long exec_referenced; int maybe_mlocked; /* found VM_LOCKED, but it's unstable result */ diff --git a/mm/rmap.c b/mm/rmap.c index b84f350..5ae7c81 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -373,6 +373,9 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) /* * Subfunctions of wipe_page_reference: wipe_page_reference_one called * repeatedly from either wipe_page_reference_anon or wipe_page_reference_file. + * + * SWAP_SUCCESS - success + * SWAP_AGAIN - give up to take lock, try later again */ int wipe_page_reference_one(struct page *page, struct page_reference_context *refctx, @@ -381,6 +384,7 @@ int wipe_page_reference_one(struct page *page, struct mm_struct *mm = vma->vm_mm; pte_t *pte; spinlock_t *ptl; + int ret = SWAP_SUCCESS; /* * Don't want to elevate referenced for mlocked page that gets this far, @@ -392,10 +396,14 @@ int wipe_page_reference_one(struct page *page, goto out; } - pte = page_check_address(page, mm, address, &ptl, 0); - if (!pte) + pte = __page_check_address(page, mm, address, &ptl, 0, + refctx->soft_try); + if (IS_ERR(pte)) { + if (PTR_ERR(pte) == -EAGAIN) { + ret = SWAP_AGAIN; + } goto out; - + } if (ptep_clear_flush_young_notify(vma, address, pte)) { /* * Don't treat a reference through a sequentially read @@ -421,7 +429,7 @@ int wipe_page_reference_one(struct page *page, pte_unmap_unlock(pte, ptl); out: - return SWAP_SUCCESS; + return ret; } static int wipe_page_reference_anon(struct page *page, diff --git a/mm/vmscan.c b/mm/vmscan.c index a01cf5e..c235059 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1329,6 +1329,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, int ret; struct page_reference_context refctx = { .is_page_locked = 0, + .soft_try = (priority < DEF_PRIORITY - 2) ? 0 : 1, }; cond_resched(); -- 1.6.5.2
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