On Thu, Jan 13, 2022 at 10:06:14AM +0000, Daniel P. Berrangé wrote:
> On Thu, Jan 13, 2022 at 02:48:15PM +0800, Peter Xu wrote:
> > On Thu, Jan 06, 2022 at 07:13:39PM -0300, Leonardo Bras wrote:
> > > @@ -558,15 +575,26 @@ static ssize_t qio_channel_socket_writev(QIOChannel
> > > *ioc,
> > > memcpy(CMSG_DATA(cmsg), fds, fdsize);
> > > }
> > >
> > > + if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {
> > > + sflags = MSG_ZEROCOPY;
> > > + }
> > > +
> > > retry:
> > > - ret = sendmsg(sioc->fd, &msg, 0);
> > > + ret = sendmsg(sioc->fd, &msg, sflags);
> > > if (ret <= 0) {
> > > - if (errno == EAGAIN) {
> > > + switch (errno) {
> > > + case EAGAIN:
> > > return QIO_CHANNEL_ERR_BLOCK;
> > > - }
> > > - if (errno == EINTR) {
> > > + case EINTR:
> > > goto retry;
> > > + case ENOBUFS:
> > > + if (sflags & MSG_ZEROCOPY) {
> > > + error_setg_errno(errp, errno,
> > > + "Process can't lock enough memory for
> > > using MSG_ZEROCOPY");
> > > + return -1;
> > > + }
> >
> > I have no idea whether it'll make a real differnece, but - should we better
> > add
> > a "break" here? If you agree and with that fixed, feel free to add:
> >
> > Reviewed-by: Peter Xu <pet...@redhat.com>
> >
> > I also wonder whether you hit ENOBUFS in any of the environments. On Fedora
> > here it's by default unlimited, but just curious when we should keep an eye.
>
> Fedora doesn't allow unlimited locked memory by default
>
> $ grep "locked memory" /proc/self/limits
> Max locked memory 65536 65536 bytes
>
> And regardless of Fedora defaults, libvirt will set a limit
> for the guest. It will only be unlimited if requiring certain
> things like VFIO.
Thanks, I obviously checked up the wrong host..
Leo, do you know how much locked memory will be needed by zero copy? Will
there be a limit? Is it linear to the number of sockets/channels?
It'll be better if we can fail at enabling the feature when we detected that
the specified locked memory limit may not be suffice.
--
Peter Xu
