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Date: Mon, 25 May 2009 14:29:29 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] Do we need CONFIG_AIO?
Message-ID: <20090525122929.GA16576@lst.de>
References: <20090525082151.GA4107@lst.de> <4A1A85B4.3060200@eu.citrix.com>
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Christoph Hellwig <hch@lst.de>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On Mon, May 25, 2009 at 12:49:08PM +0100, Stefano Stabellini wrote:
> > Currently all aio code in the raw-posix block driver depends on a
> > CONFIG_AIO symbol that gets set based on the availability of the
> > pthreads library.  Beeing able to rely on unconditional aio support
> > means we could remove the whole code for plain bdrv_read/bdrv_write
> > in raw-posix.c which is about 300 lines of code and a duplicated code
> > path.  Is there any Posix-ish platform qemu supports that does not
> > have pthreads support?
> > 
> 
> MiniOS.
> I would appreciate if you keep that flag.

I can't find MiniOS mentioned anywhere in the qemu tree.  From googling
around it seems to be some Xen demo kernel.  Do you plan to merge
support for it one day?  And what's the use case for qemu on MiniOS?
If it's anything performance sensitive the lack of aio will cause quite
severe stalling of the guest.