Re: [Qemu-devel] [PATCH 6/6] experimental native preadv/pwritev support for Linux

[Blue Swirl <blauwirbel@gmail.com>]

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On 3/15/09, Christoph Hellwig <hch@lst.de> wrote:
> On Sun, Mar 15, 2009 at 04:36:16PM +0200, Blue Swirl wrote:
>  > On 3/14/09, Christoph Hellwig <hch@lst.de> wrote:
>  > >
>  > >
>  > >  This ties up Gerd Hoffmann's unmegred preadv/pwritev syscalls to qemu.  Use with
>  > >  care as the syscall numbers aren't finalized yet.
>  > >
>  > >  If someone of the BSD folks is interested it should be trivial to tie this up
>  > >  for the preadv/pwritev syscalls that have been around there for a while.
>  >
>  > At least OpenBSD has preadv & pwritev.
>
>
> NetBSD also.  But I don't have setup of either one, so I'll need some
>  help on that front.
>
>
>  > I'd add a check to configure to see if preadv exist and then define
>  > HAVE_PREADV. Though it's not possible to see if the kernel supports
>  > preadv if libc support does not exist (checking features by running
>  > programs breaks cross compilation).
>
>
> The way glibc does it is only enable it if the underlying interface
>  exists, and then have another shortcut if it exists in the headers
>  but isn't supported by the underlying kernel.  That's what I'll try
>  to implement.

This patch adds a check for preadv, it does not find it on Linux but
does on OpenBSD.

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