From: Andy Lutomirski <luto@amacapital.net>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: mmap_sem contention issues
Date: Mon, 26 Nov 2012 12:12:16 -0800 [thread overview]
Message-ID: <CALCETrW=0gQMBW=nLKCWS-O7H5q6zYFCbFGOcC2PTS668=Z_NA@mail.gmail.com> (raw)
I'm having serious latency problems due to mmap_sem contention. I
have a real-time thread that has (soft) page faults on locked pages,
and it blocks for multiple milliseconds on
(call_rwsem_down_read_failed do_page_fault page_fault). Can this be
fixed?
Some ideas:
1. Drop mmap_sem during the filesystem part of mmap and munmap.
(MAP_POPULATE in particular is a disaster -- using it will easily
increase latency from a few milliseconds to a respectable fraction of
a second.)
2. Come up with some way to lock specific vm_area_structs for read
access without taking mmap_sem at all. This looks unpleasant with the
current rbtree structure -- something like a radix tree might work
much better if the nodes were to contain their own locks.
--Andy
--
Andy Lutomirski
AMA Capital Management, LLC
--
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>
reply other threads:[~2012-11-26 20:12 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
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='CALCETrW=0gQMBW=nLKCWS-O7H5q6zYFCbFGOcC2PTS668=Z_NA@mail.gmail.com' \
--to=luto@amacapital.net \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.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