From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f50.google.com (mail-ee0-f50.google.com [74.125.83.50]) by kanga.kvack.org (Postfix) with ESMTP id 0798C6B0035 for ; Wed, 7 May 2014 05:33:54 -0400 (EDT) Received: by mail-ee0-f50.google.com with SMTP id e51so529233eek.9 for ; Wed, 07 May 2014 02:33:54 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id v2si15791607eel.106.2014.05.07.02.33.52 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 07 May 2014 02:33:53 -0700 (PDT) Message-ID: <5369FDFE.20508@suse.cz> Date: Wed, 07 May 2014 11:33:50 +0200 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [PATCH] mm/compaction: do not count migratepages when unnecessary References: <5363B854.3010401@suse.cz> <1399044378-3056-1-git-send-email-vbabka@suse.cz> <1399411134-k43fsr0p@n-horiguchi@ah.jp.nec.com> In-Reply-To: <1399411134-k43fsr0p@n-horiguchi@ah.jp.nec.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Andrew Morton , Hugh Dickins , gthelen@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, Mel Gorman , iamjoonsoo.kim@lge.com, cl@linux.com, Rik van Riel On 05/06/2014 11:18 PM, Naoya Horiguchi wrote: > On Fri, May 02, 2014 at 05:26:18PM +0200, Vlastimil Babka wrote: >> During compaction, update_nr_listpages() has been used to count remaining >> non-migrated and free pages after a call to migrage_pages(). The freepages >> counting has become unneccessary, and it turns out that migratepages counting >> is also unnecessary in most cases. >> >> The only situation when it's needed to count cc->migratepages is when >> migrate_pages() returns with a negative error code. Otherwise, the non-negative >> return value is the number of pages that were not migrated, which is exactly >> the count of remaining pages in the cc->migratepages list. >> >> Furthermore, any non-zero count is only interesting for the tracepoint of >> mm_compaction_migratepages events, because after that all remaining unmigrated >> pages are put back and their count is set to 0. >> >> This patch therefore removes update_nr_listpages() completely, and changes the >> tracepoint definition so that the manual counting is done only when the >> tracepoint is enabled, and only when migrate_pages() returns a negative error >> code. >> >> Furthermore, migrate_pages() and the tracepoints won't be called when there's >> nothing to migrate. This potentially avoids some wasted cycles and reduces the >> volume of uninteresting mm_compaction_migratepages events where "nr_migrated=0 >> nr_failed=0". In the stress-highalloc mmtest, this was about 75% of the events. >> The mm_compaction_isolate_migratepages event is better for determining that >> nothing was isolated for migration, and this one was just duplicating the info. > > I agree with this patch. > Reviewed-by: Naoya Horiguchi Thanks. > A few nitpicks below... > >> Signed-off-by: Vlastimil Babka >> Cc: Minchan Kim >> Cc: Mel Gorman >> Cc: Joonsoo Kim >> Cc: Naoya Horiguchi >> Cc: Christoph Lameter >> Cc: Rik van Riel >> --- >> include/trace/events/compaction.h | 26 ++++++++++++++++++++++---- >> mm/compaction.c | 30 ++++++++---------------------- >> 2 files changed, 30 insertions(+), 26 deletions(-) >> >> diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h >> index 06f544e..bbd5e1f 100644 >> --- a/include/trace/events/compaction.h >> +++ b/include/trace/events/compaction.h >> @@ -5,7 +5,9 @@ >> #define _TRACE_COMPACTION_H >> >> #include >> +#include >> #include >> +#include >> #include >> >> DECLARE_EVENT_CLASS(mm_compaction_isolate_template, >> @@ -47,10 +49,11 @@ DEFINE_EVENT(mm_compaction_isolate_template, mm_compaction_isolate_freepages, >> >> TRACE_EVENT(mm_compaction_migratepages, >> >> - TP_PROTO(unsigned long nr_migrated, >> - unsigned long nr_failed), >> + TP_PROTO(unsigned long nr_all, >> + int migrate_rc, >> + struct list_head * migratepages), > > checkpatch.pl shows code violation message for this line. > (ERROR: "foo * bar" should be "foo *bar") > >> >> - TP_ARGS(nr_migrated, nr_failed), >> + TP_ARGS(nr_all, migrate_rc, migratepages), >> >> TP_STRUCT__entry( >> __field(unsigned long, nr_migrated) >> @@ -58,7 +61,22 @@ TRACE_EVENT(mm_compaction_migratepages, >> ), >> >> TP_fast_assign( >> - __entry->nr_migrated = nr_migrated; >> + unsigned long nr_failed = 0; >> + struct page *page; >> + >> + /* >> + * migrate_pages() returns either a non-negative number >> + * with the number of pages that failed migration, or an >> + * error code, in which case we need to count the remaining >> + * pages manually >> + */ >> + if (migrate_rc >= 0) >> + nr_failed = migrate_rc; >> + else >> + list_for_each_entry(page, migratepages, lru) > > This line contains whitespace indent. Oops, will fix those checkpatchs... >> + nr_failed++; >> + >> + __entry->nr_migrated = nr_all - nr_failed; >> __entry->nr_failed = nr_failed; >> ), >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index ae1d0ae..873d7de 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -799,22 +799,6 @@ static void compaction_free(struct page *page, unsigned long data) >> cc->nr_freepages++; >> } >> >> -/* >> - * We cannot control nr_migratepages fully when migration is running as >> - * migrate_pages() has no knowledge of of compact_control. When migration is >> - * complete, we count the number of pages on the list by hand. >> - */ >> -static void update_nr_listpages(struct compact_control *cc) >> -{ >> - int nr_migratepages = 0; >> - struct page *page; >> - >> - list_for_each_entry(page, &cc->migratepages, lru) >> - nr_migratepages++; >> - >> - cc->nr_migratepages = nr_migratepages; >> -} >> - >> /* possible outcome of isolate_migratepages */ >> typedef enum { >> ISOLATE_ABORT, /* Abort compaction now */ >> @@ -1006,7 +990,6 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) >> migrate_prep_local(); >> >> while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) { >> - unsigned long nr_migrate, nr_remaining; >> int err; >> >> switch (isolate_migratepages(zone, cc)) { >> @@ -1021,16 +1004,16 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) >> ; >> } >> >> - nr_migrate = cc->nr_migratepages; >> + if (!cc->nr_migratepages) >> + continue; >> + >> err = migrate_pages(&cc->migratepages, compaction_alloc, >> compaction_free, (unsigned long)cc, >> cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC, >> MR_COMPACTION); >> - update_nr_listpages(cc); >> - nr_remaining = cc->nr_migratepages; >> >> - trace_mm_compaction_migratepages(nr_migrate - nr_remaining, >> - nr_remaining); >> + trace_mm_compaction_migratepages(cc->nr_migratepages, err, >> + &cc->migratepages); >> >> /* Release isolated pages not migrated */ >> if (err) { >> @@ -1044,6 +1027,9 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) >> ret = COMPACT_PARTIAL; >> goto out; >> } >> + } else { >> + /* All pages were successfully migrated */ >> + cc->nr_migratepages = 0; > > cc->nr_migratepages = 0 is also done in err != 0, so can it be done in common path? Well it would have to be done before 'if (err)', thus also before putback_movable_pages(), which is a bit awkward. But avoiding 'else' is also good I guess so I'll do that for next version. > Thanks, > Naoya Horiguchi > -- 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