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Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool
From: |
Andrea Arcangeli |
Subject: |
Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool |
Date: |
Fri, 12 Dec 2008 16:44:18 +0100 |
On Fri, Dec 12, 2008 at 08:35:57AM -0600, Anthony Liguori wrote:
> I've been thinking about this, the problems I see are:
>
> 1) It's impossible to accept a file descriptor for a block device (possibly
> not a problem)
What do you mean with accept? You mean to accept a tcp connection? How
would a block device fd be related to accept(2)?
> 2) You'd have to open all the file descriptors at once. Otherwise, you get
> really strange behavior if the file gets deleted while the guest is running
> (for instance, with -snapshot).
Definitely, that's what I meant with hack around the bdrv api... not
even close to nice but doable in theory. Only advantage is that it
runs on older kernels but with seeking I/O lseek has to run as well.
Now that linux-aio is out of the picture for quite a long time for us,
I guess it worth to wait preadv/pwritev and stick with that and
reconsider linux-aio after they fix it... Waiting Gerd to post a full
patch.
But it's your call... I'm fine either ways. Clearly the os missing
preadv/pwritev would need to be limited to 1 thread per fd (but 1
thread per fd kind of breaks with the current _global_ list so I guess
they'll be limited to just 1 thread otherwise it may be actually
simpler to just open the file multiple times than to have a per-fd
queue ;), not the end of the world for them.
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, (continued)
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Christoph Hellwig, 2008/12/11
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Andrea Arcangeli, 2008/12/11
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Christoph Hellwig, 2008/12/11
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Anthony Liguori, 2008/12/11
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Andrea Arcangeli, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Anthony Liguori, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool,
Andrea Arcangeli <=
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Anthony Liguori, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Andrea Arcangeli, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Anthony Liguori, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Andrea Arcangeli, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Anthony Liguori, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Andrea Arcangeli, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Gerd Hoffmann, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Anthony Liguori, 2008/12/12
- Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Gerd Hoffmann, 2008/12/12
Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Avi Kivity, 2008/12/09