Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755350AbZKNJeW (ORCPT ); Sat, 14 Nov 2009 04:34:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755205AbZKNJeV (ORCPT ); Sat, 14 Nov 2009 04:34:21 -0500 Received: from mail-iw0-f178.google.com ([209.85.223.178]:40136 "EHLO mail-iw0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755061AbZKNJeS convert rfc822-to-8bit (ORCPT ); Sat, 14 Nov 2009 04:34:18 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=hIzuQTbGst/PLqC+72bq8eBJpeAXRK/22lABsoL7lYCow/pmbq29Xn4pP81hcq0fjD zFip2l2cWaUzeig0dZDLGF2cP/+1PMsFTcNTH6ab+y4D8xGSibiP5Yr6PhE4Xxw85mGX 1fNC9ZaYnBcKmXQjW5DLIuwkKeKtFNaZnjGD0= MIME-Version: 1.0 In-Reply-To: <20091113181740.GN29804@csn.ul.ie> References: <20091113142558.33B6.A69D9226@jp.fujitsu.com> <20091113141303.GI29804@csn.ul.ie> <20091114023901.3DA8.A69D9226@jp.fujitsu.com> <20091113181740.GN29804@csn.ul.ie> Date: Sat, 14 Nov 2009 18:34:23 +0900 X-Google-Sender-Auth: 7c7a499c0467df02 Message-ID: <2f11576a0911140134u21eafa83t9642bb25ccd953de@mail.gmail.com> Subject: Re: [PATCH 4/5] vmscan: Have kswapd sleep for a short interval and double check it should be asleep From: KOSAKI Motohiro To: Mel Gorman Cc: Andrew Morton , Frans Pop , Jiri Kosina , Sven Geggus , Karol Lewandowski , Tobias Oetiker , linux-kernel@vger.kernel.org, "linux-mm@kvack.org" , Pekka Enberg , Rik van Riel , Christoph Lameter , Stephan von Krawczynski , "Rafael J. Wysocki" , Kernel Testers List Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8425 Lines: 190 2009/11/14 Mel Gorman : > On Sat, Nov 14, 2009 at 03:00:57AM +0900, KOSAKI Motohiro wrote: >> > On Fri, Nov 13, 2009 at 07:43:09PM +0900, KOSAKI Motohiro wrote: >> > > > After kswapd balances all zones in a pgdat, it goes to sleep. In the event >> > > > of no IO congestion, kswapd can go to sleep very shortly after the high >> > > > watermark was reached. If there are a constant stream of allocations from >> > > > parallel processes, it can mean that kswapd went to sleep too quickly and >> > > > the high watermark is not being maintained for sufficient length time. >> > > > >> > > > This patch makes kswapd go to sleep as a two-stage process. It first >> > > > tries to sleep for HZ/10. If it is woken up by another process or the >> > > > high watermark is no longer met, it's considered a premature sleep and >> > > > kswapd continues work. Otherwise it goes fully to sleep. >> > > > >> > > > This adds more counters to distinguish between fast and slow breaches of >> > > > watermarks. A "fast" premature sleep is one where the low watermark was >> > > > hit in a very short time after kswapd going to sleep. A "slow" premature >> > > > sleep indicates that the high watermark was breached after a very short >> > > > interval. >> > > > >> > > > Signed-off-by: Mel Gorman >> > > >> > > Why do you submit this patch to mainline? this is debugging patch >> > > no more and no less. >> > > >> > >> > Do you mean the stats part? The stats are included until such time as the page >> > allocator failure reports stop or are significantly reduced. In the event a >> > report is received, the value of the counters help determine if kswapd was >> > struggling or not. They should be removed once this mess is ironed out. >> > >> > If there is a preference, I can split out the stats part and send it to >> > people with page allocator failure reports for retesting. >> >> I'm sorry my last mail didn't have enough explanation. >> This stats help to solve this issue. I agreed. but after solving this issue, >> I don't imagine administrator how to use this stats. if KSWAPD_PREMATURE_FAST or >> KSWAPD_PREMATURE_SLOW significantly increased, what should admin do? > > One possible workaround would be to raise min_free_kbytes while a fix is > being worked on. Please correct me, if I said wrong thing. if I was admin, I don't watch this stats because kswapd frequently wakeup doesn't mean any trouble. instead I watch number of allocation failure. [see include/linux/vmstat.h] umm... Why don't we have nr-allocation-failure vmstat? I don't remember it. GFP_NOWARN failure doesn't make syslog error logging. but frequently GFP_NOWARN failure imply the system is under memory pressure or under heavy fragmentation. It is good opportunity to change min_free_kbytes. >> Or, Can LKML folk make any advise to admin? >> > > Work with them to fix the bug :/ > >> if kernel doesn't have any bug, kswapd wakeup rate is not so worth information imho. >> following your additional code itself looks good to me. but... >> >> >> > ==== CUT HERE ==== >> > vmscan: Have kswapd sleep for a short interval and double check it should be asleep fix 1 >> > >> > This patch is a fix and a claritifacation to the patch "vmscan: Have >> > kswapd sleep for a short interval and double check it should be asleep". >> > The fix is for kswapd to only check zones in the node it is responsible >> > for. The clarification is to rename two counters to better explain what is >> > being counted. >> > >> > Signed-off-by: Mel Gorman >> > --- >> > ?include/linux/vmstat.h | ? ?2 +- >> > ?mm/vmscan.c ? ? ? ? ? ?| ? 20 +++++++++++++------- >> > ?mm/vmstat.c ? ? ? ? ? ?| ? ?4 ++-- >> > ?3 files changed, 16 insertions(+), 10 deletions(-) >> > >> > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h >> > index 7d66695..0591a48 100644 >> > --- a/include/linux/vmstat.h >> > +++ b/include/linux/vmstat.h >> > @@ -40,7 +40,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, >> > ? ? ? ? ? ? PGSCAN_ZONE_RECLAIM_FAILED, >> > ?#endif >> > ? ? ? ? ? ? PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL, >> > - ? ? ? ? ? KSWAPD_PREMATURE_FAST, KSWAPD_PREMATURE_SLOW, >> > + ? ? ? ? ? KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY, >> > ? ? ? ? ? ? KSWAPD_NO_CONGESTION_WAIT, >> > ? ? ? ? ? ? PAGEOUTRUN, ALLOCSTALL, PGROTATED, >> > ?#ifdef CONFIG_HUGETLB_PAGE >> > diff --git a/mm/vmscan.c b/mm/vmscan.c >> > index 70967e1..5557555 100644 >> > --- a/mm/vmscan.c >> > +++ b/mm/vmscan.c >> > @@ -1905,19 +1905,25 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, >> > ?#endif >> > >> > ?/* is kswapd sleeping prematurely? */ >> > -static int sleeping_prematurely(int order, long remaining) >> > +static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) >> > ?{ >> > - ? struct zone *zone; >> > + ? int i; >> > >> > ? ? /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ >> > ? ? if (remaining) >> > ? ? ? ? ? ? return 1; >> > >> > ? ? /* If after HZ/10, a zone is below the high mark, it's premature */ >> > - ? for_each_populated_zone(zone) >> > + ? for (i = 0; i < pgdat->nr_zones; i++) { >> > + ? ? ? ? ? struct zone *zone = pgdat->node_zones + i; >> > + >> > + ? ? ? ? ? if (!populated_zone(zone)) >> > + ? ? ? ? ? ? ? ? ? continue; >> > + >> > ? ? ? ? ? ? if (!zone_watermark_ok(zone, order, high_wmark_pages(zone), >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0, 0)) >> > ? ? ? ? ? ? ? ? ? ? return 1; >> > + ? } >> > >> > ? ? return 0; >> > ?} >> > @@ -2221,7 +2227,7 @@ static int kswapd(void *p) >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? long remaining = 0; >> > >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? /* Try to sleep for a short interval */ >> > - ? ? ? ? ? ? ? ? ? ? ? ? ? if (!sleeping_prematurely(order, remaining)) { >> > + ? ? ? ? ? ? ? ? ? ? ? ? ? if (!sleeping_prematurely(pgdat, order, remaining)) { >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? remaining = schedule_timeout(HZ/10); >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? finish_wait(&pgdat->kswapd_wait, &wait); >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); >> > @@ -2232,13 +2238,13 @@ static int kswapd(void *p) >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?* premature sleep. If not, then go fully >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?* to sleep until explicitly woken up >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?*/ >> > - ? ? ? ? ? ? ? ? ? ? ? ? ? if (!sleeping_prematurely(order, remaining)) >> > + ? ? ? ? ? ? ? ? ? ? ? ? ? if (!sleeping_prematurely(pgdat, order, remaining)) >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? schedule(); >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? else { >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? if (remaining) >> > - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? count_vm_event(KSWAPD_PREMATURE_FAST); >> > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? else >> > - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? count_vm_event(KSWAPD_PREMATURE_SLOW); >> > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? } >> > ? ? ? ? ? ? ? ? ? ? } >> > >> > diff --git a/mm/vmstat.c b/mm/vmstat.c >> > index bc09547..6cc8dc6 100644 >> > --- a/mm/vmstat.c >> > +++ b/mm/vmstat.c >> > @@ -683,8 +683,8 @@ static const char * const vmstat_text[] = { >> > ? ? "slabs_scanned", >> > ? ? "kswapd_steal", >> > ? ? "kswapd_inodesteal", >> > - ? "kswapd_slept_prematurely_fast", >> > - ? "kswapd_slept_prematurely_slow", >> > + ? "kswapd_low_wmark_hit_quickly", >> > + ? "kswapd_high_wmark_hit_quickly", >> > ? ? "kswapd_no_congestion_wait", >> > ? ? "pageoutrun", >> > ? ? "allocstall", >> >> >> > > -- > Mel Gorman > Part-time Phd Student ? ? ? ? ? ? ? ? ? ? ? ? ?Linux Technology Center > University of Limerick ? ? ? ? ? ? ? ? ? ? ? ? IBM Dublin Software Lab > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. ?For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- 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/