Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754689Ab1EDB4f (ORCPT ); Tue, 3 May 2011 21:56:35 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:34194 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752299Ab1EDB4d (ORCPT ); Tue, 3 May 2011 21:56:33 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=kkMCbj5810jCFwH3w6dzxJWeyTxSbAhB+dwiN0qm8CQy5btoZ+o0ts768lthHjebrY XC8A+tPG0mygZQ4S2OCW0M1Wuqg7YQRLxcWfcguDlnIA/h6aei8hc0N6L6XMoNyBd6H8 J7+8llT5CruuGt3UegxP9SP+XmCFN8yZbGVBU= MIME-Version: 1.0 In-Reply-To: <20110428133644.GA12400@localhost> References: <20110426055521.GA18473@localhost> <20110426062535.GB19717@localhost> <20110426063421.GC19717@localhost> <20110426092029.GA27053@localhost> <20110426124743.e58d9746.akpm@linux-foundation.org> <20110428133644.GA12400@localhost> Date: Wed, 4 May 2011 09:56:31 +0800 Message-ID: Subject: Re: [RFC][PATCH] mm: cut down __GFP_NORETRY page allocation failures From: Dave Young To: Wu Fengguang Cc: Andrew Morton , Minchan Kim , linux-mm , Linux Kernel Mailing List , Mel Gorman , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Christoph Lameter , Dave Chinner , David Rientjes Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id p441v38J028937 Content-Length: 9162 Lines: 212 On Thu, Apr 28, 2011 at 9:36 PM, Wu Fengguang 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 > Signed-off-by: Wu Fengguang > --- >  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 ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?