From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
Cc: Michal Hocko <mhocko@suse.cz>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com
Subject: Re: [PATCH] hugeltb: Mark hugelb_max_hstate __read_mostly
Date: Fri, 22 Jun 2012 15:06:31 -0700 [thread overview]
Message-ID: <20120622150631.9a7c4d17.akpm@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1206150948120.20541@router.home>
On Fri, 15 Jun 2012 09:50:00 -0500 (CDT)
Christoph Lameter <cl@linux.com> wrote:
> On Fri, 15 Jun 2012, Michal Hocko wrote:
>
> > > Thats all? There is no performance gain from this change?
> >
> > Is that required in order to put data in the read mostly section?
>
> I thought so. The read_mostly section is specially designed for data that
> causes excessive cacheline bounces and has to be grouped with rarely
> accessed other data. That was at least the intend when we created it.
>
The __read_mostly thing really is a bit of a crapshoot. The runtime
effects are extremely dependent upon Kconfig settings and toolchain
behaviour. I do recall one or two cases where people did fix
real-world observed performance issues by adding __read_mostly.
Literally "one or two". We have more than one or two __read_mostly
annotations in there!
As that hugelb_max_hstate is write-once, it's a good candidate. I'll
apply the patch and hope that it improves someone's kernel somewhere
someday. Shrug.
--
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/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2012-06-22 22:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-14 13:56 [PATCH] hugeltb: Mark hugelb_max_hstate __read_mostly Aneesh Kumar K.V
2012-06-14 14:12 ` Michal Hocko
2012-06-14 20:43 ` Christoph Lameter
2012-06-15 6:08 ` Aneesh Kumar K.V
2012-06-15 13:57 ` Christoph Lameter
2012-06-15 14:33 ` Michal Hocko
2012-06-15 14:50 ` Christoph Lameter
2012-06-22 22:06 ` Andrew Morton [this message]
2012-06-15 6:10 ` Aneesh Kumar K.V
2012-06-22 22:03 ` 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=20120622150631.9a7c4d17.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=aneesh.kumar@linux.vnet.ibm.com \
--cc=cl@linux.com \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.cz \
/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).