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From: Mel Gorman <mgorman@suse.de>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Johannes Weiner <jweiner@redhat.com>,
	Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 3/3] compaction accouting fix
Date: Fri, 2 Sep 2011 14:36:48 +0100	[thread overview]
Message-ID: <20110902133648.GP14369@suse.de> (raw)
In-Reply-To: <CAEwNFnCSgPj+KuZr0h9-0=mr29QDYnFDzvtwV5Vc1VBVtThqWA@mail.gmail.com>

On Fri, Sep 02, 2011 at 02:09:55PM +0900, Minchan Kim wrote:
> On Thu, Sep 1, 2011 at 11:20 PM, Mel Gorman <mgorman@suse.de> wrote:
> > On Sun, Nov 13, 2011 at 01:37:43AM +0900, Minchan Kim wrote:
> >> I saw the following accouting of compaction during test of the series.
> >
> > s/accouting/accounting/ both here and in the subject. A nicer name the
> > patch would have been
> >
> > "mm: compaction: Only update compact_blocks_moved if compaction was successful"
> 
> Thanks, I will fix it at next version. :)
> 
> >
> >>
> >> compact_blocks_moved 251
> >> compact_pages_moved 44
> >>
> >> It's very awkward to me although it's possbile because it means we try to compact 251 blocks
> >> but it just migrated 44 pages. As further investigation, I found isolate_migratepages doesn't
> >> isolate any pages but it returns ISOLATE_SUCCESS and then, it just increases compact_blocks_moved
> >> but doesn't increased compact_pages_moved.
> >>
> >> This patch makes accouting of compaction works only in case of success of isolation.
> >>
> >
> > compact_blocks_moved exists to indicate the rate compaction is
> > scanning pageblocks. If compact_blocks_moved and compact_pages_moved
> > are increasing at a similar rate for example, it could imply that
> > compaction is doing a lot of scanning but is not necessarily useful
> > work. It's not necessarily reflected by compact_fail because that
> > counter is only updated for pages that were isolated from the LRU.
> 
> You seem to say "compact_pagemigrate_failed" not "compact_fail".
> 

I did. Thanks.

> >
> > I now recognise of course that "compact_blocks_moved" was an *awful*
> > choice of name for this stat.
> 
> I hope changing stat names as follows unless it's too late(ie, it
> doesn't break ABI with any tools)
> 

I'm not aware of any tools that depend on this except my own reporting
scripts and even those do not particularly care.

> compact_blocks_moved -> compact_blocks

compact_pageblock_scanned?

> compact_pages_moved -> compact_pgmigrated_success
> compact_pagemigrate_failed -> compact_pgmigrated_fail
> compact_stall -> compact_alloc_stall
> compact_fail -> compact_alloc_fail
> compact_success -> compact_alloc_success
> 

Seems reasonable to me.

-- 
Mel Gorman
SUSE Labs

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      reply	other threads:[~2011-09-02 13:36 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-11-12 16:37 [PATCH 0/3] Fix compaction about mlocked pages Minchan Kim
2011-08-29 16:43 ` [PATCH 3/3] compaction accouting fix Minchan Kim
2011-08-29 16:43 ` [PATCH 1/3] Correct isolate_mode_t bitwise type Minchan Kim
2011-08-29 16:43 ` [PATCH 2/3] compaction: compact unevictable page Minchan Kim
2011-10-06 21:54 ` [PATCH 0/3] Fix compaction about mlocked pages Andrew Morton
2011-10-06 23:07   ` Minchan Kim
2011-11-12 16:37 ` [PATCH 1/3] Correct isolate_mode_t bitwise type Minchan Kim
2011-08-30 17:51   ` Rik van Riel
2011-08-31 11:13   ` Johannes Weiner
2011-09-01 13:05   ` Mel Gorman
2011-09-02  3:29     ` Minchan Kim
2011-11-12 16:37 ` [PATCH 2/3] compaction: compact unevictable page Minchan Kim
2011-08-31  1:09   ` Rik van Riel
2011-08-31 11:19   ` Johannes Weiner
2011-08-31 14:41     ` Minchan Kim
2011-09-01 14:02       ` Mel Gorman
2011-09-02  4:48         ` Minchan Kim
2011-09-02 13:34           ` Mel Gorman
2011-11-12 16:37 ` [PATCH 3/3] compaction accouting fix Minchan Kim
2011-08-31 11:37   ` Johannes Weiner
2011-08-31 14:56     ` Minchan Kim
2011-08-31 15:03       ` Johannes Weiner
2011-09-01 14:20   ` Mel Gorman
2011-09-02  5:09     ` Minchan Kim
2011-09-02 13:36       ` Mel Gorman [this message]

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