From: Andrew Morton <akpm@osdl.org>
To: Andrea Arcangeli <andrea@suse.de>
Cc: hugh@veritas.com, torvalds@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: anon-vma (and now filebacked-mappings too) mprotect vma merging [Re: 2.6.5-rc2-aa vma merging]
Date: Sat, 3 Apr 2004 17:13:58 -0800 [thread overview]
Message-ID: <20040403171358.5dec3987.akpm@osdl.org> (raw)
In-Reply-To: <20040404010147.GS2307@dualathlon.random>
Andrea Arcangeli <andrea@suse.de> wrote:
>
> BTW, now that the lookup on the
> prio-tree is immediate the i_shared_sem has no reason anymore to be a
> semaphore either, it should go back to a spinlock like in 2.4, like the
> anon_vma is also protected by a spinlock.
That change was made for scheduling latency reasons, mainly due to huge
pagetable walks in zap_page_range():
i_shared_lock is held for a very long time during vmtruncate() and
causes high scheduling latencies when truncating a file which is
mmapped. I've seen 100 milliseconds.
So turn it into a semaphore. It nests inside mmap_sem. This
change is also needed by the shared pagetable patch, which needs to
unshare pte's on the vmtruncate path - lots of pagetable pages need to
be allocated and they are using __GFP_WAIT.
If we no longer hold that lock during pte takedown then sure, it would
be better if we had a spinlock in there.
next prev parent reply other threads:[~2004-04-04 1:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.44.0403291957240.19124-100000@localhost.localdomain>
2004-03-29 19:45 ` 2.6.5-rc2-aa vma merging Hugh Dickins
2004-04-02 11:34 ` Hugh Dickins
2004-04-02 15:35 ` Andrea Arcangeli
2004-04-03 1:26 ` anon-vma (and now filebacked-mappings too) mprotect vma merging [Re: 2.6.5-rc2-aa vma merging] Andrea Arcangeli
2004-04-03 17:06 ` Hugh Dickins
2004-04-03 17:24 ` Andrea Arcangeli
2004-04-03 18:46 ` Andrea Arcangeli
2004-04-03 19:29 ` Hugh Dickins
2004-04-04 1:01 ` Andrea Arcangeli
2004-04-04 1:13 ` Andrew Morton [this message]
2004-04-04 1:32 ` Andrea Arcangeli
2004-04-04 1:43 ` Andrew Morton
2004-04-04 1:55 ` Andrea Arcangeli
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=20040403171358.5dec3987.akpm@osdl.org \
--to=akpm@osdl.org \
--cc=andrea@suse.de \
--cc=hugh@veritas.com \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@osdl.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 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.