From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Andrew Morton <akpm@osdl.org>
Cc: hugh@veritas.com, andrea@suse.de, linux-kernel@vger.kernel.org
Subject: Re: smp race fix between invalidate_inode_pages* and do_no_page
Date: Fri, 13 Jan 2006 21:37:39 +1100 [thread overview]
Message-ID: <43C782F3.1090803@yahoo.com.au> (raw)
In-Reply-To: <20060112234726.676c3873.akpm@osdl.org>
Andrew Morton wrote:
> Nick Piggin <nickpiggin@yahoo.com.au> wrote:
>
>>(I guess reclaim might be one, but quite rare -- any other significant
>> lock_page users that we might hit?)
>
>
> The only time 2.6 holds lock_page() for a significant duration is when
> bringing the page uptodate with readpage or memset.
>
Yes that's what I thought. And we don't really need to worry about this
case because filemap_nopage has to deal with it anyway (ie. we shouldn't
see a locked !uptodate page in do_no_page).
> The scalability risk here is 100 CPUs all faulting in the same file in the
> same pattern. Like the workload which caused the page_table_lock splitup
> (that was with anon pages). All the CPUs could pretty easily get into sync
> and start arguing over every single page's lock.
>
Yes, but in that case they're still going to hit the tree_lock anyway, and
if they do have a chance of synching up, the cacheline bouncing from count
and mapcount accounting is almost as likely to cause it as the lock_page
itself.
I did a nopage microbenchmark like you describe a while back. IIRC single
threaded is 2.5 times *more* throughput than 64 CPUs, even when those 64 are
faulting their own NUMA memory (and obviously different pages). Thanks to
tree_lock.
--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com
next prev parent reply other threads:[~2006-01-13 10:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-13 19:37 smp race fix between invalidate_inode_pages* and do_no_page Andrea Arcangeli
2005-12-13 21:02 ` Andrew Morton
2005-12-13 21:14 ` Andrea Arcangeli
2005-12-16 13:51 ` Andrea Arcangeli
2006-01-10 6:24 ` Andrea Arcangeli
2006-01-10 6:48 ` Andrea Arcangeli
2006-01-11 4:08 ` Nick Piggin
2006-01-11 8:23 ` Andrea Arcangeli
2006-01-11 8:51 ` Andrew Morton
2006-01-11 9:02 ` Andrea Arcangeli
2006-01-11 9:06 ` Andrew Morton
2006-01-11 9:13 ` Andrea Arcangeli
2006-01-11 20:49 ` Hugh Dickins
2006-01-11 21:05 ` Andrew Morton
2006-01-13 7:35 ` Nick Piggin
2006-01-13 7:47 ` Andrew Morton
2006-01-13 10:37 ` Nick Piggin [this message]
2006-03-31 12:36 ` Andrea Arcangeli
2006-04-02 5:17 ` Nick Piggin
2006-04-02 5:21 ` Andrew Morton
2006-04-07 19:18 ` Hugh Dickins
2006-01-11 9:39 ` Nick Piggin
2006-01-11 9:34 ` Nick Piggin
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=43C782F3.1090803@yahoo.com.au \
--to=nickpiggin@yahoo.com.au \
--cc=akpm@osdl.org \
--cc=andrea@suse.de \
--cc=hugh@veritas.com \
--cc=linux-kernel@vger.kernel.org \
/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).