Re: hacking - aio_sendfile()
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On Thu, Jul 11, 2013 at 11:44:32AM -0700, Scott Long wrote:
>=20
> On Jul 10, 2013, at 11:17 PM, Konstantin Belousov <kostikbel@gmail.com> w=
rote:
>=20
> > On Wed, Jul 10, 2013 at 04:36:23PM -0700, Adrian Chadd wrote:
> >> Hiya,
> >>=20
> >> I've started writing an aio_sendfile() syscall.
> >>=20
> >> http://people.freebsd.org/~adrian/ath/20130710-aio-sendfile-3.diff
> >>=20
> >> Yes, the diff is against -HEAD and not stable/9.
> >>=20
> >> It's totally horrible, hackish and likely bad. I've only done some
> >> very, very basic testing to ensure it actually works; i haven't at all
> >> stress tested it out yet. It's also very naive - I'm not at all doing
> >> any checks to see whether I can short-cut to do the aio there and
> >> then; I'm always queuing the sendfile() op through the worker threads.
> >> That's likely stupid and inefficient in a lot of cases, but it at
> >> least gets the syscall up and working.
> > Yes, it is naive, but for different reason.
> >=20
> > The kern_sendfile() is synchronous function, it only completes after
> > the other end of the network communication allows it. This means
> > that calling kern_sendfile() from the aio thread blocks the thread
> > indefinitely by unbounded sleep.
>=20
>=20
> No, kern_sendfile is async unless you specify the SF_SYNC hack flag.
> Otherwise, it'll fill the socket buffer and then return immediately, unle=
ss
> the socket buffer is full and the socket is set to blocking mode. That's
> outside the scope, as I said in my previous email.
You do not understand what I said, please re-read both my mail and code
before replying. Implementing aio_sendfile() as proposed would create
yet another possibility of indefinitely block all processes using aio.
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