On Thu, Jul 11, 2013 at 11:44:32AM -0700, Scott Long wrote: > > On Jul 10, 2013, at 11:17 PM, Konstantin Belousov <kostikbel_at_gmail.com> wrote: > > > On Wed, Jul 10, 2013 at 04:36:23PM -0700, Adrian Chadd wrote: > >> Hiya, > >> > >> I've started writing an aio_sendfile() syscall. > >> > >> http://people.freebsd.org/~adrian/ath/20130710-aio-sendfile-3.diff > >> > >> Yes, the diff is against -HEAD and not stable/9. > >> > >> 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. > > > > 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. > > > No, kern_sendfile is async unless you specify the SF_SYNC hack flag. > Otherwise, it'll fill the socket buffer and then return immediately, unless > 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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