From: Christoph Lameter <cl@linux.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>, Shaohua Li <shaohua.li@intel.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
David Rientjes <rientjes@google.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low
Date: Tue, 9 Nov 2010 10:48:13 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.00.1011091006280.9898@router.home> (raw)
In-Reply-To: <20101029124002.356bd592.akpm@linux-foundation.org>
On Fri, 29 Oct 2010, Andrew Morton wrote:
> > To match the existing maximum which I assume is due to the deltas being
> > stored in a s8.
>
> hm, OK. So (CHAR_MAX-2) would be a tad clearer, only there's no
> CHAR_MAX and "2" remains mysterious ;)
inc/dec_zone_page_state first increments (allows compiler to generate a
RMV instruction, hmmm... there we could use this cpu....) and then checks
if we are beyond the threshold. So the maximum value has to be below
CHAR_MAX. 125 is the next value that looks somewhat sane as a limit. We
could use CHAR_MAX if we change the comparison logic for the threshhold.
> I do go on about code comments a lot lately. Eric D's kernel just
> crashed because we didn't adequately comment first_zones_zonelist()
> so I'm feeling all vindicated!
We should not have done the change to add the nodemask to
first_zones_zonelist but instead added a new function. Now the function
has two different ways of behaving.
> I don't really buy that. The cache footprint will be increased by a
> max of one cacheline (for zone->stat_threshold) and the cache footprint
> will be actually reduced in the much larger percpu area (depending on
> alignment and padding and stuff).
It will increase by one cacheline per zone in use. Large systems have lots
of zones which increases the effect.
The vmstat functions are often used as primitives in various critical code
paths. The cache footprint needs to be kept as low as possible.
--
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 policy in Canada: sign http://dissolvethecrtc.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2010-11-09 16:48 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-28 15:13 [PATCH 0/2] Reduce the amount of time spent in watermark-related functions V4 Mel Gorman
2010-10-28 15:13 ` [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low Mel Gorman
2010-10-28 22:04 ` Andrew Morton
2010-10-29 10:12 ` Mel Gorman
2010-10-29 19:40 ` Andrew Morton
2010-11-02 0:53 ` Shaohua Li
2010-11-09 11:33 ` Mel Gorman
2010-11-09 16:48 ` Christoph Lameter [this message]
2010-10-29 14:58 ` Christoph Lameter
2010-10-29 18:25 ` Andrew Morton
2010-10-29 19:33 ` Christoph Lameter
2010-10-28 15:13 ` [PATCH 2/2] mm: vmstat: Use a single setter function and callback for adjusting percpu thresholds Mel Gorman
2010-10-28 22:09 ` Andrew Morton
2010-10-29 10:17 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-10-27 8:47 [PATCH 0/2] Reduce the amount of time spent in watermark-related functions Mel Gorman
2010-10-27 8:47 ` [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low Mel Gorman
2010-10-27 20:16 ` Christoph Lameter
2010-10-28 1:09 ` KAMEZAWA Hiroyuki
2010-10-28 9:49 ` Mel Gorman
2010-10-28 9:58 ` KAMEZAWA Hiroyuki
2010-11-01 7:06 ` KOSAKI Motohiro
2010-11-26 16:06 ` Kyle McMartin
2010-11-29 9:56 ` Mel Gorman
2010-11-29 13:16 ` Kyle McMartin
2010-11-29 15:08 ` Mel Gorman
2010-11-29 15:22 ` Kyle McMartin
2010-11-29 15:26 ` Kyle McMartin
2010-11-29 15:58 ` Mel Gorman
2010-12-23 22:18 ` David Rientjes
2010-12-23 22:35 ` Andrew Morton
2010-12-23 23:00 ` Kyle McMartin
2010-12-23 23:07 ` David Rientjes
2010-12-23 23:17 ` 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=alpine.DEB.2.00.1011091006280.9898@router.home \
--to=cl@linux.com \
--cc=akpm@linux-foundation.org \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
--cc=rientjes@google.com \
--cc=shaohua.li@intel.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).