From: Manfred Spraul <manfreds@colorfullife.com>
To: Alexander Viro <viro@math.psu.edu>
Cc: "Stephen C. Tweedie" <sct@redhat.com>,
Andrea Arcangeli <andrea@suse.de>,
linux-kernel@vger.rutgers.edu,
Ingo Molnar <mingo@chiara.csoma.elte.hu>,
linux-mm@kvack.org
Subject: Re: locking question: do_mmap(), do_munmap()
Date: Tue, 12 Oct 1999 00:13:37 +0200 [thread overview]
Message-ID: <38026111.DB88AEA7@colorfullife.com> (raw)
In-Reply-To: <Pine.GSO.4.10.9910111733310.18777-100000@weyl.math.psu.edu>
Alexander Viro wrote:
> What does it buy you over the simple semaphore here? Do you really see a
> contention scenario?
I think you are right, I see no case where a normal semaphore would
lock-up and the rw semaphore would not lock up.
we win something _if_ vm_ops->swapout() is extremely slow:
* with lock_kernel() [ie currently], multiple threads can sleep within
vm_ops->swapout() of the same "struct mm"
* an rw-semaphore would mimic that behaviour.
* a normal semaphore would prevent that.
I'm not sure if it is worth to implement a rw-semaphore, especially
since we win something in a very obscure case, but we loose cpu-cycles
for every down_rw()/up_rw() [there is no 2 asm-instruction rw-semaphore]
--
Manfred
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://humbolt.geo.uu.nl/Linux-MM/
next prev parent reply other threads:[~1999-10-11 22:13 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.10.9910101713010.364-100000@alpha.random>
1999-10-10 15:52 ` Manfred Spraul
1999-10-10 16:07 ` Alexander Viro
1999-10-10 16:25 ` Alexander Viro
1999-10-10 16:45 ` Manfred Spraul
1999-10-10 17:25 ` Alexander Viro
1999-10-10 17:12 ` Andrea Arcangeli
1999-10-10 17:48 ` Alexander Viro
1999-10-10 18:42 ` Manfred Spraul
1999-10-10 19:03 ` Alexander Viro
1999-10-10 21:31 ` Manfred Spraul
1999-10-10 21:53 ` Andrea Arcangeli
1999-10-10 22:34 ` Alexander Viro
1999-10-10 23:28 ` Andrea Arcangeli
1999-10-11 15:50 ` Stephen C. Tweedie
1999-10-11 16:05 ` Alexander Viro
1999-10-11 18:02 ` Manfred Spraul
1999-10-11 19:07 ` Kanoj Sarcar
1999-10-11 22:23 ` Stephen C. Tweedie
1999-10-13 1:25 ` Kanoj Sarcar
1999-10-13 7:32 ` Manfred Spraul
1999-10-15 9:58 ` Ralf Baechle
1999-10-15 17:50 ` Kanoj Sarcar
1999-10-13 10:45 ` Stephen C. Tweedie
1999-10-11 20:15 ` Stephen C. Tweedie
1999-10-11 21:14 ` Manfred Spraul
1999-10-11 21:37 ` Alexander Viro
1999-10-11 22:13 ` Manfred Spraul [this message]
1999-10-11 22:22 ` Stephen C. Tweedie
1999-10-11 23:01 ` Alexander Viro
1999-10-12 14:06 ` [more fun] " Alexander Viro
1999-10-13 7:35 ` Manfred Spraul
1999-10-13 18:34 ` Kanoj Sarcar
1999-10-13 10:16 ` Stephen C. Tweedie
1999-10-11 20:13 ` Stephen C. Tweedie
1999-10-11 21:40 ` Alexander Viro
1999-10-11 22:20 ` Stephen C. Tweedie
1999-10-11 22:31 ` Alexander Viro
1999-10-13 10:25 ` Stephen C. Tweedie
1999-10-11 15:47 ` Stephen C. Tweedie
1999-10-11 15:43 ` Stephen C. Tweedie
1999-10-10 16:56 ` Andrea Arcangeli
1999-10-11 15:41 ` Stephen C. Tweedie
1999-10-11 15:52 ` Alexander Viro
1999-10-09 12:48 Manfred Spraul
1999-10-09 13:12 ` Alexander Viro
1999-10-09 13:17 ` Manfred Spraul
1999-10-09 13:38 ` Alexander Viro
1999-10-09 16:01 ` Andrea Arcangeli
1999-10-10 13:05 ` Manfred Spraul
1999-10-11 15:09 ` Stephen C. Tweedie
1999-10-11 15:05 ` Stephen C. Tweedie
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=38026111.DB88AEA7@colorfullife.com \
--to=manfreds@colorfullife.com \
--cc=andrea@suse.de \
--cc=linux-kernel@vger.rutgers.edu \
--cc=linux-mm@kvack.org \
--cc=mingo@chiara.csoma.elte.hu \
--cc=sct@redhat.com \
--cc=viro@math.psu.edu \
/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