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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 19:26:34 +0100 |
On Fri, Dec 12, 2008 at 12:17:58PM -0600, Anthony Liguori wrote:
> You assume that anything using bdrv_aio_readv/writev will be going through
> a DMA API. This isn't a safe assumption.
Well it's obviously a safe assumption right now... ;)
I've an hard time seeing any 'metadata' (because _data_ will be
guaranteed to always pass through the dma api if it wants to be
vectored) being physically contiguous on disk but not contiguous on
ram.
> Furthermore, you need some way to communicate the fact that you cannot
> handle iovcnt > 1 iovecs in a performant/safe way.
assert(iovcnt == 1) will work fine. If somebody changes some backend
like qcow2 to call bdrv_aio_readv/writev they'll get an assert and
they'll ask for a compatibility layer. I don't see any urgency to add
it immediately and I think assert(iovcnt==1) is more preferable until
any user emerges asking for bdrv_aio_readv/writev as it'll function as
a debug trap to be sure all works right.
- 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, 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, 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, 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, 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
Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool, Ian Jackson, 2008/12/17