From: Andrea Arcangeli <aarcange@redhat.com>
To: qemu-devel@nongnu.org
Cc: Gerd Hoffmann <kraxel@redhat.com>, kvm-devel <kvm@vger.kernel.org>
Subject: Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool
Date: Wed, 10 Dec 2008 17:44:01 +0100 [thread overview]
Message-ID: <20081210164401.GF18814@random.random> (raw)
In-Reply-To: <493E965E.5050701@us.ibm.com>
On Tue, Dec 09, 2008 at 10:01:34AM -0600, Anthony Liguori wrote:
> Yes, that's what I'm going to do before committing it.
I've been hacking on this too, just to push out a full tested patchset
without the _em badness... problem is if we use more than one thread,
there's a thread race between lseek and writev, pread/pwrite don't
have the issue as they store the pos on the kernel stack, and they
don't pass through the shared file->f_pos. We'd really need
preadv/pwritev...
To solve this in userland without kernel aio we'd need to open (not
just dup) the file in each thread, then the file->f_pos will become
thread local and we can cache the last lseek value and avoid the lseek
syscall for contiguous I/O. Or we need to reduce the number of threads
to 1 per fd (screwing seeking I/O). kernel aio wouldn't have this
trouble and a single fd/file would be enough, but that would only work
on linux.
next prev parent reply other threads:[~2008-12-10 16:44 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-05 21:21 [RFC] Replace posix-aio with custom thread pool Anthony Liguori
2008-12-05 21:21 ` [Qemu-devel] " Anthony Liguori
2008-12-06 9:03 ` Blue Swirl
2008-12-06 18:26 ` Jamie Lokier
2008-12-08 18:23 ` Anthony Liguori
2008-12-08 18:23 ` Anthony Liguori
2008-12-09 15:51 ` Gerd Hoffmann
2008-12-09 16:01 ` Anthony Liguori
2008-12-10 16:44 ` Andrea Arcangeli [this message]
2008-12-10 17:21 ` Anthony Liguori
2008-12-10 17:21 ` Anthony Liguori
2008-12-10 17:29 ` Gerd Hoffmann
2008-12-10 18:50 ` Anthony Liguori
2008-12-10 19:08 ` Andrea Arcangeli
2008-12-10 19:08 ` Andrea Arcangeli
2008-12-11 13:12 ` Andrea Arcangeli
2008-12-11 15:24 ` Gerd Hoffmann
2008-12-11 15:24 ` Gerd Hoffmann
2008-12-11 15:53 ` Andrea Arcangeli
2008-12-11 15:53 ` Andrea Arcangeli
2008-12-11 16:11 ` Gerd Hoffmann
2008-12-11 16:11 ` Gerd Hoffmann
2008-12-11 16:49 ` Andrea Arcangeli
2008-12-11 16:49 ` Andrea Arcangeli
2008-12-11 17:20 ` Gerd Hoffmann
2008-12-11 17:20 ` Gerd Hoffmann
2008-12-11 18:11 ` Andrea Arcangeli
2008-12-11 18:11 ` Andrea Arcangeli
2008-12-11 20:38 ` Gerd Hoffmann
2008-12-11 20:38 ` Gerd Hoffmann
2008-12-11 20:40 ` Anthony Liguori
2008-12-12 8:23 ` Jens Axboe
2008-12-12 8:23 ` Jens Axboe
2008-12-12 11:51 ` Andrea Arcangeli
2008-12-12 11:51 ` Andrea Arcangeli
2008-12-12 11:54 ` Jens Axboe
2008-12-12 11:54 ` Jens Axboe
2008-12-12 14:13 ` Andrea Arcangeli
2008-12-12 14:13 ` Andrea Arcangeli
2008-12-12 14:24 ` Anthony Liguori
2008-12-12 14:24 ` Anthony Liguori
2008-12-12 16:33 ` Chris Wright
2008-12-12 16:33 ` Chris Wright
2008-12-12 16:51 ` Anthony Liguori
2008-12-12 16:51 ` Anthony Liguori
2008-12-12 16:52 ` Chris Wright
2008-12-12 16:52 ` Chris Wright
2008-12-11 21:32 ` Christoph Hellwig
2008-12-12 0:27 ` Andrea Arcangeli
2008-12-12 0:27 ` Andrea Arcangeli
2008-12-11 21:30 ` Christoph Hellwig
2008-12-11 16:41 ` Anthony Liguori
2008-12-11 16:41 ` Anthony Liguori
2008-12-12 14:24 ` Andrea Arcangeli
2008-12-12 14:24 ` Andrea Arcangeli
2008-12-12 14:35 ` Anthony Liguori
2008-12-12 14:35 ` Anthony Liguori
2008-12-12 15:44 ` Andrea Arcangeli
2008-12-12 15:44 ` Andrea Arcangeli
2008-12-12 16:49 ` Anthony Liguori
2008-12-12 16:49 ` Anthony Liguori
2008-12-12 17:09 ` Andrea Arcangeli
2008-12-12 17:09 ` Andrea Arcangeli
2008-12-12 17:25 ` Anthony Liguori
2008-12-12 17:25 ` Anthony Liguori
2008-12-12 17:52 ` Andrea Arcangeli
2008-12-12 17:52 ` Andrea Arcangeli
2008-12-12 18:17 ` Anthony Liguori
2008-12-12 18:17 ` Anthony Liguori
2008-12-12 18:26 ` Andrea Arcangeli
2008-12-12 20:12 ` Gerd Hoffmann
2008-12-12 20:17 ` Anthony Liguori
2008-12-12 20:35 ` Gerd Hoffmann
2008-12-09 17:16 ` Avi Kivity
2008-12-17 14:44 ` Ian Jackson
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