From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53143) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e1yQG-0001Sf-LB for qemu-devel@nongnu.org; Tue, 10 Oct 2017 13:34:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e1yQC-00018z-Ma for qemu-devel@nongnu.org; Tue, 10 Oct 2017 13:34:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46534) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e1yQC-00018j-De for qemu-devel@nongnu.org; Tue, 10 Oct 2017 13:34:24 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 76A717E448 for ; Tue, 10 Oct 2017 17:34:23 +0000 (UTC) Date: Tue, 10 Oct 2017 18:34:19 +0100 From: "Daniel P. Berrange" Message-ID: <20171010173419.GA18266@redhat.com> Reply-To: "Daniel P. Berrange" References: <20171010154328.8419-1-berrange@redhat.com> <20171010154328.8419-3-berrange@redhat.com> <5622c2ab-caa8-3c46-0926-c46218a3d179@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5622c2ab-caa8-3c46-0926-c46218a3d179@redhat.com> Subject: Re: [Qemu-devel] [PATCH v1 2/7] io: simplify websocket ping reply handling List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org On Tue, Oct 10, 2017 at 11:55:25AM -0500, Eric Blake wrote: > On 10/10/2017 10:43 AM, Daniel P. Berrange wrote: > > We must ensure we don't get flooded with ping replies if the outbound > > channel is slow. Currently we do this by keeping the ping reply in a > > separate temporary buffer and only writing it if the encoutput buffer > > is completely empty. This is overly pessimistic, as it is reasonable > > to add a ping reply to the encoutput buffer even if it has previous > > data in it, as long as that previous data doesn't include a ping > > reply. > > > > To track this better, put the ping reply directly into the encoutput > > buffer, and then record the size of encoutput at this time in > > ping_remain. As we write encoutput to the underlying channel, we > > can decrement the ping_remain counter. Once it hits zero, we can > > accept further ping replies for transmission. > > > > Signed-off-by: Daniel P. Berrange > > --- > > include/io/channel-websock.h | 2 +- > > io/channel-websock.c | 28 +++++++++++++++------------- > > 2 files changed, 16 insertions(+), 14 deletions(-) > > > > > +++ b/io/channel-websock.c > > @@ -825,11 +825,14 @@ static int qio_channel_websock_decode_payload(QIOChannelWebsock *ioc, > > } > > return -1; > > } else if (ioc->opcode == QIO_CHANNEL_WEBSOCK_OPCODE_PING) { > > - /* ping frames produce an immediate reply */ > > - buffer_reset(&ioc->ping_reply); > > - qio_channel_websock_encode_buffer( > > - ioc, &ioc->ping_reply, QIO_CHANNEL_WEBSOCK_OPCODE_PONG, > > - &ioc->encinput); > > + /* ping frames produce an immediate reply, as long as we've not still > > + * got a previous ping queued, in which case we drop the new pong */ > > Wouldn't that be a 'previous pong queued'? Indeed > > > + if (ioc->ping_remain == 0) { > > + qio_channel_websock_encode_buffer( > > + ioc, &ioc->encoutput, QIO_CHANNEL_WEBSOCK_OPCODE_PONG, > > + &ioc->encinput); > > + ioc->ping_remain = ioc->encoutput.offset; > > + } > > But if you change the comment, then naming the variable pong_remain may > make more sense. Yeah, that's sensible. > > But naming is a bikeshed issue, so either way, > > Reviewed-by: Eric Blake Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|