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Message-ID: <BANLkTimpT-N5--3QjcNg8CyNNwfEWxFyKA@mail.gmail.com>
Date: Wed, 4 May 2011 09:56:31 +0800
From: Dave Young <hidave.darkstar@...il.com>
To: Wu Fengguang <fengguang.wu@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Minchan Kim <minchan.kim@...il.com>,
linux-mm <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Mel Gorman <mel@...ux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Christoph Lameter <cl@...ux.com>,
Dave Chinner <david@...morbit.com>,
David Rientjes <rientjes@...gle.com>
Subject: Re: [RFC][PATCH] mm: cut down __GFP_NORETRY page allocation failures
On Thu, Apr 28, 2011 at 9:36 PM, Wu Fengguang <fengguang.wu@...el.com> wrote:
> 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
>
With Core2 Duo, 3G ram, No swap partition I can not produce the alloc fail
> 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
Could you tell how to get above info?
>
> 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
>
> this patch (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
>
> CC: Mel Gorman <mel@...ux.vnet.ibm.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
> mm/page_alloc.c | 17 +++--------------
> mm/vmscan.c | 6 ++++++
> 2 files changed, 9 insertions(+), 14 deletions(-)
> --- linux-next.orig/mm/vmscan.c 2011-04-28 21:16:16.000000000 +0800
> +++ linux-next/mm/vmscan.c 2011-04-28 21:28:57.000000000 +0800
> @@ -1978,6 +1978,8 @@ static void shrink_zones(int priority, s
> continue;
> if (zone->all_unreclaimable && priority != DEF_PRIORITY)
> continue; /* Let kswapd poll it */
> + sc->nr_to_reclaim = max(sc->nr_to_reclaim,
> + zone->watermark[WMARK_HIGH]);
> }
>
> shrink_zone(priority, zone, sc);
> @@ -2034,6 +2036,7 @@ 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();
> @@ -2067,6 +2070,9 @@ static unsigned long do_try_to_free_page
> }
> }
> total_scanned += sc->nr_scanned;
> + if (sc->nr_reclaimed >= min_reclaim &&
> + total_scanned > 2 * sc->nr_to_reclaim)
> + goto out;
> if (sc->nr_reclaimed >= sc->nr_to_reclaim)
> goto out;
>
> --- linux-next.orig/mm/page_alloc.c 2011-04-28 21:16:16.000000000 +0800
> +++ linux-next/mm/page_alloc.c 2011-04-28 21:16:18.000000000 +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();
>
> @@ -1912,22 +1911,12 @@ __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;
> }
>
>
--
Regards
dave
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