From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: Stuart Anderson <anderson@netsweng.com>
Subject: Re: [Qemu-devel] RFC: x86_64 Best way to fix 'cast to pointer from integer of different size' problems?
Date: Tue, 6 Nov 2007 22:05:34 +0000 [thread overview]
Message-ID: <200711062205.34944.paul@codesourcery.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0711061648570.17870@trantor.stuart.netsweng.com>
> By the time you consider the different combinations of targets & hosts,
> most of the opportunities for zero copy are eliminated anyway. Byte
> ordering and structure packing amd content differences mean that we can't
> do zero-copy except in the rare circumstance that the host & target
> match is all of these respects. The read & write buffers would still
> benefit from zero copy, but nearly everything else has to be touched
> anyway.
If you're not careful you get double-copying. Once copying the struct from
guest to host space, and then again when converting layout/endianess.
I've no idea whether this overhead is important in practice though.
Paul
next prev parent reply other threads:[~2007-11-06 22:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-03 17:26 [Qemu-devel] RFC: x86_64 Best way to fix 'cast to pointer from integer of different size' problems? TJ
2007-11-03 17:52 ` Paul Brook
2007-11-05 19:51 ` Thayne Harbaugh
2007-11-06 1:05 ` Paul Brook
2007-11-06 2:00 ` Thayne Harbaugh
2007-11-07 19:18 ` Fabrice Bellard
2007-11-07 20:59 ` Thayne Harbaugh
2007-11-07 23:02 ` Paul Brook
2007-11-12 16:42 ` Thayne Harbaugh
2007-11-06 20:05 ` Fabrice Bellard
2007-11-06 21:52 ` Stuart Anderson
2007-11-06 22:05 ` Paul Brook [this message]
2007-11-06 22:19 ` Stuart Anderson
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