From: Mel Gorman <mgorman@suse.de>
To: Huang Shijie <b32955@freescale.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org, shijie8@gmail.com
Subject: Re: [PATCH v2] mm/compaction : fix the wrong return value for isolate_migratepages()
Date: Thu, 5 Jan 2012 10:12:22 +0000 [thread overview]
Message-ID: <20120105101222.GD28031@suse.de> (raw)
In-Reply-To: <1325322585-16216-1-git-send-email-b32955@freescale.com>
On Sat, Dec 31, 2011 at 05:09:45PM +0800, Huang Shijie wrote:
> When we do not get any migrate page, we should return ISOLATE_NONE.
>
Why?
Returning ISOLATE_SUCCESS means that we fall through. This means busy
work in migrate_pages(), updating list accounting and the list. It's
wasteful but is it functionally incorrect? What problem did you observe?
If this is simply a performance issue then minimally COMPACTBLOCKS
still needs to be updated, we still want to see the tracepoint etc. To
preserve that, I would suggest as an alternative to leave it returning
ISOLATE_SUCCESS but move
err = migrate_pages(&cc->migratepages, compaction_alloc,
(unsigned long)cc, false,
cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC);
update_nr_listpages(cc);
inside a if (nr_migrate) check to avoid some overhead.
--
Mel Gorman
SUSE Labs
--
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/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2012-01-05 10:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-31 9:09 [PATCH v2] mm/compaction : fix the wrong return value for isolate_migratepages() Huang Shijie
2012-01-05 10:12 ` Mel Gorman [this message]
2012-01-05 10:31 ` Huang Shijie
2012-01-05 10:50 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120105101222.GD28031@suse.de \
--to=mgorman@suse.de \
--cc=akpm@linux-foundation.org \
--cc=b32955@freescale.com \
--cc=linux-mm@kvack.org \
--cc=shijie8@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).