On Thu, Feb 04, 2021 at 04:20:18PM -0600, Eric Blake wrote: > Our default of a backlog of 1 connection is rather puny, particularly > for scenarios where we expect multiple listeners to connect (such as > qemu-nbd -e X). For Unix sockets, there's no real harm in supporting > a larger backlog, and a definite benefit to the clients: at least on > Linux, a client trying to connect to a Unix socket with a backlog gets > an EAGAIN failure with no way to poll() for when the backlog is no > longer present short of sleeping an arbitrary amount of time before > retrying. > > See https://bugzilla.redhat.com/1925045 for a demonstration of where > our low backlog prevents libnbd from connecting as many parallel > clients as it wants. > > Reported-by: Richard W.M. Jones <rjo...@redhat.com> > Signed-off-by: Eric Blake <ebl...@redhat.com> > --- > util/qemu-sockets.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c > index 8af0278f15c6..a7573e9f0fda 100644 > --- a/util/qemu-sockets.c > +++ b/util/qemu-sockets.c > @@ -1059,7 +1059,7 @@ int unix_listen(const char *str, Error **errp) > > saddr = g_new0(UnixSocketAddress, 1); > saddr->path = g_strdup(str); > - sock = unix_listen_saddr(saddr, 1, errp); > + sock = unix_listen_saddr(saddr, SOMAXCONN, errp); > qapi_free_UnixSocketAddress(saddr); > return sock; > }
Does this fix the problem with qemu-nbd? Not for me - I still seem to see the old behaviour with this patch applied. Also looking more generally at util/qemu-sockets.c I think it would be better if all of those "num" parameters were renamed "backlog". Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org
