From: Andrew Morton <akpm@linux-foundation.org>
To: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
linux-mm@kvack.org, Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH 3/3] mm: take pagevecs off reclaim stack
Date: Thu, 29 Dec 2011 19:59:17 -0800 [thread overview]
Message-ID: <20111229195917.13f15974.akpm@linux-foundation.org> (raw)
In-Reply-To: <alpine.LSU.2.00.1112291753350.3614@eggly.anvils>
On Thu, 29 Dec 2011 17:55:14 -0800 (PST) Hugh Dickins <hughd@google.com> wrote:
> > However, at that time, I think this patch behave
> > better than old. If we release and retake zone lock per 14 pages,
> > other tasks can easily steal a part of lumpy reclaimed pages. and then
> > long latency wrongness will be happen when system is under large page
> > memory allocation pressure. That's the reason why I posted very similar patch
> > a long time ago.
>
> Aha, and another good point. Thank you.
I hope you understand it better than I :(
Long lock hold times and long irq-off times are demonstrable problems
which have hurt people in the past. Whereas the someone-stole-my-page
issue is theoretical, undemonstrated and unquantified. And for
some people, lengthy worst-case latency is a serious problem, doesn't
matter whether the system is under memory pressure or not - that simply
determines when the worst-case hits.
This is not all some handwavy theoretical thing either. If we've gone
and introduced serious latency issues, people *will* hit them and treat
it as a regression.
Now, a way out here is to remove lumpy reclaim (please). And make the
problem not come back by promising to never call putback_lru_pages(lots
of pages) (how do we do this?).
So I think the best way ahead here is to distribute this patch in the
same release in which we remove lumpy reclaim (pokes Mel).
--
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:[~2011-12-30 3:55 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-29 4:32 [PATCH 0/3] mm: three minor vmscan improvements Hugh Dickins
2011-12-29 4:35 ` [PATCH 1/3] mm: test PageSwapBacked in lumpy reclaim Hugh Dickins
2011-12-29 5:06 ` KOSAKI Motohiro
2012-01-04 1:23 ` Minchan Kim
2012-01-05 6:03 ` KAMEZAWA Hiroyuki
2011-12-29 4:36 ` [PATCH 2/3] mm: cond_resched in scan_mapping_unevictable_pages Hugh Dickins
2011-12-29 5:14 ` KOSAKI Motohiro
2011-12-29 5:48 ` Hugh Dickins
2011-12-29 22:46 ` Hugh Dickins
2011-12-29 4:39 ` [PATCH 3/3] mm: take pagevecs off reclaim stack Hugh Dickins
2011-12-29 5:42 ` KOSAKI Motohiro
2011-12-29 11:18 ` Konstantin Khlebnikov
2011-12-29 22:20 ` Hugh Dickins
2011-12-29 22:55 ` Andrew Morton
2011-12-29 23:27 ` Hugh Dickins
2011-12-30 0:24 ` KOSAKI Motohiro
2011-12-30 1:55 ` Hugh Dickins
2011-12-30 3:59 ` Andrew Morton [this message]
2011-12-30 15:51 ` Mel Gorman
2012-01-01 7:18 ` Hugh Dickins
2012-01-03 23:12 ` Andrew Morton
2012-01-03 23:17 ` KOSAKI Motohiro
2012-01-03 23:29 ` Andrew Morton
2012-01-04 0:03 ` KOSAKI Motohiro
2012-01-04 3:22 ` Hugh Dickins
2012-01-04 20:20 ` Andrew Morton
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=20111229195917.13f15974.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=hughd@google.com \
--cc=khlebnikov@openvz.org \
--cc=kosaki.motohiro@gmail.com \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.