Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752596Ab1D3ORt (ORCPT ); Sat, 30 Apr 2011 10:17:49 -0400 Received: from mga11.intel.com ([192.55.52.93]:8050 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750978Ab1D3ORq (ORCPT ); Sat, 30 Apr 2011 10:17:46 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,293,1301900400"; d="scan'208";a="686360017" Date: Sat, 30 Apr 2011 22:17:41 +0800 From: Wu Fengguang To: Andrew Morton , Mel Gorman Cc: Minchan Kim , Dave Young , linux-mm , Linux Kernel Mailing List , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Christoph Lameter , Dave Chinner , David Rientjes Subject: Re: [RFC][PATCH] mm: cut down __GFP_NORETRY page allocation failures Message-ID: <20110430141741.GA4511@localhost> References: <20110426062535.GB19717@localhost> <20110426063421.GC19717@localhost> <20110426092029.GA27053@localhost> <20110426124743.e58d9746.akpm@linux-foundation.org> <20110428133644.GA12400@localhost> <20110429022824.GA8061@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110429022824.GA8061@localhost> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 17616 Lines: 485 On Fri, Apr 29, 2011 at 10:28:24AM +0800, Wu Fengguang wrote: > > Test results: > > > > - the failure rate is pretty sensible to the page reclaim size, > > from 282 (WMARK_HIGH) to 704 (WMARK_MIN) to 10496 (SWAP_CLUSTER_MAX) > > > > - the IPIs are reduced by over 100 times > > It's reduced by 500 times indeed. > > CAL: 220449 220246 220372 220558 220251 219740 220043 219968 Function call interrupts > CAL: 93 463 410 540 298 282 272 306 Function call interrupts > > > base kernel: vanilla 2.6.39-rc3 + __GFP_NORETRY readahead page allocation patch > > ------------------------------------------------------------------------------- > > nr_alloc_fail 10496 > > allocstall 1576602 > > > patched (WMARK_MIN) > > ------------------- > > nr_alloc_fail 704 > > allocstall 105551 > > > patched (WMARK_HIGH) > > -------------------- > > nr_alloc_fail 282 > > allocstall 53860 > > > this patch (WMARK_HIGH, limited scan) > > ------------------------------------- > > nr_alloc_fail 276 > > allocstall 54034 > > There is a bad side effect though: the much reduced "allocstall" means > each direct reclaim will take much more time to complete. A simple solution > is to terminate direct reclaim after 10ms. I noticed that an 100ms > time threshold can reduce the reclaim latency from 621ms to 358ms. > Further lowering the time threshold to 20ms does not help reducing the > real latencies though. Experiments going on... I tried the more reasonable terminate condition: stop direct reclaim when the preferred zone is above high watermark (see the below chunk). This helps reduce the average reclaim latency to under 100ms in the 1000-dd case. However nr_alloc_fail is around 5000 and not ideal. The interesting thing is, even if zone watermark is high, the task still may fail to get a free page.. @@ -2067,8 +2072,17 @@ static unsigned long do_try_to_free_page } } total_scanned += sc->nr_scanned; - if (sc->nr_reclaimed >= sc->nr_to_reclaim) - goto out; + if (sc->nr_reclaimed >= min_reclaim) { + if (sc->nr_reclaimed >= sc->nr_to_reclaim) + goto out; + if (total_scanned > 2 * sc->nr_to_reclaim) + goto out; + if (preferred_zone && + zone_watermark_ok_safe(preferred_zone, sc->order, + high_wmark_pages(preferred_zone), + zone_idx(preferred_zone), 0)) + goto out; + } /* * Try to write back as many pages as we just scanned. This Thanks, Fengguang --- Subject: mm: cut down __GFP_NORETRY page allocation failures Date: Thu Apr 28 13:46:39 CST 2011 Concurrent page allocations are suffering from high failure rates. On a 8p, 3GB ram test box, when reading 1000 sparse files of size 1GB, the page allocation failures are nr_alloc_fail 733 # interleaved reads by 1 single task nr_alloc_fail 11799 # concurrent reads by 1000 tasks The concurrent read test script is: for i in `seq 1000` do truncate -s 1G /fs/sparse-$i dd if=/fs/sparse-$i of=/dev/null & done In order for get_page_from_freelist() to get free page, (1) try_to_free_pages() should use much higher .nr_to_reclaim than the current SWAP_CLUSTER_MAX=32, in order to draw the zone out of the possible low watermark state as well as fill the pcp with enough free pages to overflow its high watermark. (2) the get_page_from_freelist() _after_ direct reclaim should use lower watermark than its normal invocations, so that it can reasonably "reserve" some free pages for itself and prevent other concurrent page allocators stealing all its reclaimed pages. Some notes: - commit 9ee493ce ("mm: page allocator: drain per-cpu lists after direct reclaim allocation fails") has the same target, however is obviously costly and less effective. It seems more clean to just remove the retry and drain code than to retain it. - it's a bit hacky to reclaim more than requested pages inside do_try_to_free_page(), and it won't help cgroup for now - it only aims to reduce failures when there are plenty of reclaimable pages, so it stops the opportunistic reclaim when scanned 2 times pages Test results: - the failure rate is pretty sensible to the page reclaim size, from 282 (WMARK_HIGH) to 704 (WMARK_MIN) to 10496 (SWAP_CLUSTER_MAX) - the IPIs are reduced by over 100 times base kernel: vanilla 2.6.39-rc3 + __GFP_NORETRY readahead page allocation patch ------------------------------------------------------------------------------- nr_alloc_fail 10496 allocstall 1576602 slabs_scanned 21632 kswapd_steal 4393382 kswapd_inodesteal 124 kswapd_low_wmark_hit_quickly 885 kswapd_high_wmark_hit_quickly 2321 kswapd_skip_congestion_wait 0 pageoutrun 29426 CAL: 220449 220246 220372 220558 220251 219740 220043 219968 Function call interrupts LOC: 536274 532529 531734 536801 536510 533676 534853 532038 Local timer interrupts RES: 3032 2128 1792 1765 2184 1703 1754 1865 Rescheduling interrupts TLB: 189 15 13 17 64 294 97 63 TLB shootdowns patched (WMARK_MIN) ------------------- nr_alloc_fail 704 allocstall 105551 slabs_scanned 33280 kswapd_steal 4525537 kswapd_inodesteal 187 kswapd_low_wmark_hit_quickly 4980 kswapd_high_wmark_hit_quickly 2573 kswapd_skip_congestion_wait 0 pageoutrun 35429 CAL: 93 286 396 754 272 297 275 281 Function call interrupts LOC: 520550 517751 517043 522016 520302 518479 519329 517179 Local timer interrupts RES: 2131 1371 1376 1269 1390 1181 1409 1280 Rescheduling interrupts TLB: 280 26 27 30 65 305 134 75 TLB shootdowns patched (WMARK_HIGH) -------------------- nr_alloc_fail 282 allocstall 53860 slabs_scanned 23936 kswapd_steal 4561178 kswapd_inodesteal 0 kswapd_low_wmark_hit_quickly 2760 kswapd_high_wmark_hit_quickly 1748 kswapd_skip_congestion_wait 0 pageoutrun 32639 CAL: 93 463 410 540 298 282 272 306 Function call interrupts LOC: 513956 510749 509890 514897 514300 512392 512825 510574 Local timer interrupts RES: 1174 2081 1411 1320 1742 2683 1380 1230 Rescheduling interrupts TLB: 274 21 19 22 57 317 131 61 TLB shootdowns patched (WMARK_HIGH, limited scan) ---------------------------------- nr_alloc_fail 276 allocstall 54034 slabs_scanned 24320 kswapd_steal 4507482 kswapd_inodesteal 262 kswapd_low_wmark_hit_quickly 2638 kswapd_high_wmark_hit_quickly 1710 kswapd_skip_congestion_wait 0 pageoutrun 32182 CAL: 69 443 421 567 273 279 269 334 Function call interrupts LOC: 514736 511698 510993 514069 514185 512986 513838 511229 Local timer interrupts RES: 2153 1556 1126 1351 3047 1554 1131 1560 Rescheduling interrupts TLB: 209 26 20 15 71 315 117 71 TLB shootdowns patched (WMARK_HIGH, limited scan, stop on watermark OK), 100 dd ---------------------------------------------------------------- start time: 3 total time: 50 nr_alloc_fail 162 allocstall 45523 CPU count real total virtual total delay total 921 3024540200 3009244668 37123129525 IO count delay total delay average 0 0 0ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 357 4891766796 13ms dd: read=0, write=0, cancelled_write=0 patched (WMARK_HIGH, limited scan, stop on watermark OK), 1000 dd ----------------------------------------------------------------- start time: 272 total time: 509 nr_alloc_fail 3913 allocstall 541789 CPU count real total virtual total delay total 1044 3445476208 3437200482 229919915202 IO count delay total delay average 0 0 0ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 452 34691441605 76ms dd: read=0, write=0, cancelled_write=0 patched (WMARK_HIGH, limited scan, stop on watermark OK, no time limit), 1000 dd -------------------------------------------------------------------------------- start time: 278 total time: 513 nr_alloc_fail 4737 allocstall 436392 CPU count real total virtual total delay total 1024 3371487456 3359441487 225088210977 IO count delay total delay average 1 160631171 160ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 367 30809994722 83ms dd: read=20480, write=0, cancelled_write=0 no cond_resched(): start time: 263 total time: 516 nr_alloc_fail 5144 allocstall 436787 CPU count real total virtual total delay total 1018 3305497488 3283831119 241982934044 IO count delay total delay average 0 0 0ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 328 31398481378 95ms dd: read=0, write=0, cancelled_write=0 zone_watermark_ok_safe(): start time: 266 total time: 513 nr_alloc_fail 4526 allocstall 440246 CPU count real total virtual total delay total 1119 3640446568 3619184439 240945024724 IO count delay total delay average 3 303620082 101ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 372 27320731898 73ms dd: read=77824, write=0, cancelled_write=0 start time: 275 total time: 517 nr_alloc_fail 4694 allocstall 431021 CPU count real total virtual total delay total 1073 3534462680 3512544928 234056498221 IO count delay total delay average 0 0 0ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 386 34751778363 89ms dd: read=0, write=0, cancelled_write=0 CC: Mel Gorman Signed-off-by: Wu Fengguang --- fs/buffer.c | 4 ++-- include/linux/swap.h | 3 ++- mm/page_alloc.c | 20 +++++--------------- mm/vmscan.c | 31 +++++++++++++++++++++++-------- 4 files changed, 32 insertions(+), 26 deletions(-) --- linux-next.orig/mm/vmscan.c 2011-04-29 10:42:14.000000000 +0800 +++ linux-next/mm/vmscan.c 2011-04-30 21:59:33.000000000 +0800 @@ -2025,8 +2025,9 @@ static bool all_unreclaimable(struct zon * returns: 0, if no pages reclaimed * else, the number of pages reclaimed */ -static unsigned long do_try_to_free_pages(struct zonelist *zonelist, - struct scan_control *sc) +static unsigned long do_try_to_free_pages(struct zone *preferred_zone, + struct zonelist *zonelist, + struct scan_control *sc) { int priority; unsigned long total_scanned = 0; @@ -2034,6 +2035,7 @@ static unsigned long do_try_to_free_page struct zoneref *z; struct zone *zone; unsigned long writeback_threshold; + unsigned long min_reclaim = sc->nr_to_reclaim; get_mems_allowed(); delayacct_freepages_start(); @@ -2041,6 +2043,9 @@ static unsigned long do_try_to_free_page if (scanning_global_lru(sc)) count_vm_event(ALLOCSTALL); + if (preferred_zone) + sc->nr_to_reclaim += preferred_zone->watermark[WMARK_HIGH]; + for (priority = DEF_PRIORITY; priority >= 0; priority--) { sc->nr_scanned = 0; if (!priority) @@ -2067,8 +2072,17 @@ static unsigned long do_try_to_free_page } } total_scanned += sc->nr_scanned; - if (sc->nr_reclaimed >= sc->nr_to_reclaim) - goto out; + if (sc->nr_reclaimed >= min_reclaim) { + if (sc->nr_reclaimed >= sc->nr_to_reclaim) + goto out; + if (total_scanned > 2 * sc->nr_to_reclaim) + goto out; + if (preferred_zone && + zone_watermark_ok_safe(preferred_zone, sc->order, + high_wmark_pages(preferred_zone), + zone_idx(preferred_zone), 0)) + goto out; + } /* * Try to write back as many pages as we just scanned. This @@ -2117,7 +2131,8 @@ out: return 0; } -unsigned long try_to_free_pages(struct zonelist *zonelist, int order, +unsigned long try_to_free_pages(struct zone *preferred_zone, + struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *nodemask) { unsigned long nr_reclaimed; @@ -2137,7 +2152,7 @@ unsigned long try_to_free_pages(struct z sc.may_writepage, gfp_mask); - nr_reclaimed = do_try_to_free_pages(zonelist, &sc); + nr_reclaimed = do_try_to_free_pages(preferred_zone, zonelist, &sc); trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); @@ -2207,7 +2222,7 @@ unsigned long try_to_free_mem_cgroup_pag sc.may_writepage, sc.gfp_mask); - nr_reclaimed = do_try_to_free_pages(zonelist, &sc); + nr_reclaimed = do_try_to_free_pages(NULL, zonelist, &sc); trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); @@ -2796,7 +2811,7 @@ unsigned long shrink_all_memory(unsigned reclaim_state.reclaimed_slab = 0; p->reclaim_state = &reclaim_state; - nr_reclaimed = do_try_to_free_pages(zonelist, &sc); + nr_reclaimed = do_try_to_free_pages(NULL, zonelist, &sc); p->reclaim_state = NULL; lockdep_clear_current_reclaim_state(); --- linux-next.orig/mm/page_alloc.c 2011-04-29 10:42:15.000000000 +0800 +++ linux-next/mm/page_alloc.c 2011-04-30 21:29:40.000000000 +0800 @@ -1888,9 +1888,8 @@ __alloc_pages_direct_reclaim(gfp_t gfp_m nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone, int migratetype, unsigned long *did_some_progress) { - struct page *page = NULL; + struct page *page; struct reclaim_state reclaim_state; - bool drained = false; cond_resched(); @@ -1901,7 +1900,8 @@ __alloc_pages_direct_reclaim(gfp_t gfp_m reclaim_state.reclaimed_slab = 0; current->reclaim_state = &reclaim_state; - *did_some_progress = try_to_free_pages(zonelist, order, gfp_mask, nodemask); + *did_some_progress = try_to_free_pages(preferred_zone, zonelist, order, + gfp_mask, nodemask); current->reclaim_state = NULL; lockdep_clear_current_reclaim_state(); @@ -1912,22 +1912,12 @@ __alloc_pages_direct_reclaim(gfp_t gfp_m if (unlikely(!(*did_some_progress))) return NULL; -retry: + alloc_flags |= ALLOC_HARDER; + page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist, high_zoneidx, alloc_flags, preferred_zone, migratetype); - - /* - * If an allocation failed after direct reclaim, it could be because - * pages are pinned on the per-cpu lists. Drain them and try again - */ - if (!page && !drained) { - drain_all_pages(); - drained = true; - goto retry; - } - return page; } --- linux-next.orig/fs/buffer.c 2011-04-30 13:26:57.000000000 +0800 +++ linux-next/fs/buffer.c 2011-04-30 13:29:08.000000000 +0800 @@ -288,8 +288,8 @@ static void free_more_memory(void) gfp_zone(GFP_NOFS), NULL, &zone); if (zone) - try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, - GFP_NOFS, NULL); + try_to_free_pages(zone, node_zonelist(nid, GFP_NOFS), + 0, GFP_NOFS, NULL); } } --- linux-next.orig/include/linux/swap.h 2011-04-30 13:30:36.000000000 +0800 +++ linux-next/include/linux/swap.h 2011-04-30 13:31:03.000000000 +0800 @@ -249,7 +249,8 @@ static inline void lru_cache_add_file(st #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */ /* linux/mm/vmscan.c */ -extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order, +extern unsigned long try_to_free_pages(struct zone *preferred_zone, + struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *mask); extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem, gfp_t gfp_mask, bool noswap, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/