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Date: Mon, 12 May 2014 11:51:35 +0200 From: Vlastimil Babka <vbabka@...e.cz> To: Michal Nazarewicz <mina86@...a86.com>, Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com> CC: Hugh Dickins <hughd@...gle.com>, Greg Thelen <gthelen@...gle.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>, Joonsoo Kim <iamjoonsoo.kim@....com>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>, Christoph Lameter <cl@...ux.com>, Rik van Riel <riel@...hat.com> Subject: Re: [PATCH v2 1/2] mm/compaction: do not count migratepages when unnecessary On 05/09/2014 05:48 PM, Michal Nazarewicz wrote: > On Wed, May 07 2014, 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. >> >> Signed-off-by: Vlastimil Babka <vbabka@...e.cz> >> Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com> >> Cc: Minchan Kim <minchan@...nel.org> >> Cc: Mel Gorman <mgorman@...e.de> >> Cc: Joonsoo Kim <iamjoonsoo.kim@....com> >> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com> >> Cc: Michal Nazarewicz <mina86@...a86.com> > > Acked-by: Michal Nazarewicz <mina86@...a86.com> > > One tiny comment below: > >> Cc: Christoph Lameter <cl@...ux.com> >> Cc: Rik van Riel <riel@...hat.com> >> --- >> v2: checkpack and other non-functional fixes suggested by Naoya Horiguchi >> >> include/trace/events/compaction.h | 26 ++++++++++++++++++++++---- >> mm/compaction.c | 31 +++++++------------------------ >> 2 files changed, 29 insertions(+), 28 deletions(-) >> >> diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h >> index 06f544e..aacaf0f 100644 >> --- a/include/trace/events/compaction.h >> +++ b/include/trace/events/compaction.h >> @@ -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) >> + nr_failed++; > > list_for_each would suffice here. > >> + >> + __entry->nr_migrated = nr_all - nr_failed; >> __entry->nr_failed = nr_failed; >> ), >> Right, thanks! -----8<----- From: Vlastimil Babka <vbabka@...e.cz> Date: Mon, 12 May 2014 10:56:11 +0200 Subject: [PATCH] mm-compaction-do-not-count-migratepages-when-unnecessary-fix list_for_each is enough for counting the list length. We also avoid including struct page definition this way. Suggested-by: Michal Nazarewicz <mina86@...a86.com> Signed-off-by: Vlastimil Babka <vbabka@...e.cz> --- include/trace/events/compaction.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h index aacaf0f..c6814b9 100644 --- a/include/trace/events/compaction.h +++ b/include/trace/events/compaction.h @@ -7,7 +7,6 @@ #include <linux/types.h> #include <linux/list.h> #include <linux/tracepoint.h> -#include <linux/mm_types.h> #include <trace/events/gfpflags.h> DECLARE_EVENT_CLASS(mm_compaction_isolate_template, @@ -62,7 +61,7 @@ TRACE_EVENT(mm_compaction_migratepages, TP_fast_assign( unsigned long nr_failed = 0; - struct page *page; + struct list_head *page_lru; /* * migrate_pages() returns either a non-negative number @@ -73,7 +72,7 @@ TRACE_EVENT(mm_compaction_migratepages, if (migrate_rc >= 0) nr_failed = migrate_rc; else - list_for_each_entry(page, migratepages, lru) + list_for_each(page_lru, migratepages) nr_failed++; __entry->nr_migrated = nr_all - nr_failed; -- 1.8.4.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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