On 2/8/21 4:00 AM, Daniel P. Berrangé wrote: > On Fri, Feb 05, 2021 at 12:57:05PM -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). This is especially important for Unix sockets, as a >> definite benefit to 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> >> --- >> >> v2: target the correct API used by qemu-nbd, rather than an unrelated >> legacy wrapper [Dan] >> >> qemu-nbd.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/qemu-nbd.c b/qemu-nbd.c >> index 608c63e82a25..cd20ee73be19 100644 >> --- a/qemu-nbd.c >> +++ b/qemu-nbd.c >> @@ -965,7 +965,8 @@ int main(int argc, char **argv) >> server = qio_net_listener_new(); >> if (socket_activation == 0) { >> saddr = nbd_build_socket_address(sockpath, bindto, port); >> - if (qio_net_listener_open_sync(server, saddr, 1, &local_err) < 0) { >> + if (qio_net_listener_open_sync(server, saddr, SOMAXCONN, >> + &local_err) < 0) { > > This addresses qemu-nbd, but surely we want to be consistent with the > QMP nbd-server-start impl too, in blockdev-nbd.c >
Good point, I'll send v3. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
