On Fri, Sep 02, 2011 at 02:09:55PM +0900, Minchan Kim wrote:

On Thu, Sep 1, 2011 at 11:20 PM, Mel Gorman [off-list ref] wrote:

quoted

On Sun, Nov 13, 2011 at 01:37:43AM +0900, Minchan Kim wrote:

quoted

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. :)

quoted

quoted

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.

quoted

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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