svn commit: r241931 - in head/sys: conf kern

Andre Oppermann andre at freebsd.org
Tue Oct 23 15:28:01 UTC 2012


On 23.10.2012 17:11, David Chisnall wrote:
> On 23 Oct 2012, at 16:05, Andre Oppermann wrote:
>
>> For zero copy send we're trying to come up with a sendfile-like
>> approach where the page is simply wired into kernel space.  The
>> application then is not allowed to touch it until the socket
>> buffer has released it again.  The main issue here is how to
>> provide feedback to the application when it is safe for reuse.
>
> It's been a few years since I used it, but I thought that aio_write() already provided this.  The application may not modify the contents of the memory pointed to by aio_buf until after it has received notification that the write has finished.  This happens either via a signal directly, a signal polled by kqueue, or a call to aio_return().

Indeed, that's one of the ways being explored.  It requires the
explicit cooperation of the application.  I don't think there is
any way around that.

-- 
Andre



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