From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38752) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zf7oZ-0003wf-Mw for qemu-devel@nongnu.org; Thu, 24 Sep 2015 10:48:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zf7oV-0006jJ-I7 for qemu-devel@nongnu.org; Thu, 24 Sep 2015 10:48:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47195) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zf7oV-0006jC-DJ for qemu-devel@nongnu.org; Thu, 24 Sep 2015 10:47:59 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 17BAD2FAA64 for ; Thu, 24 Sep 2015 14:47:59 +0000 (UTC) Date: Thu, 24 Sep 2015 15:47:55 +0100 From: "Daniel P. Berrange" Message-ID: <20150924144755.GG31980@redhat.com> References: <1442582350-9179-1-git-send-email-berrange@redhat.com> <1442582350-9179-8-git-send-email-berrange@redhat.com> <5601474F.2000507@redhat.com> <20150922122452.GN28888@redhat.com> <56014969.4070603@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <56014969.4070603@redhat.com> Subject: Re: [Qemu-devel] [PATCH v1 07/16] io: add abstract QIOChannel classes Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Gerd Hoffmann , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" On Tue, Sep 22, 2015 at 02:28:25PM +0200, Paolo Bonzini wrote: > > > On 22/09/2015 14:24, Daniel P. Berrange wrote: > > On Tue, Sep 22, 2015 at 02:19:27PM +0200, Paolo Bonzini wrote: > >> > >> > >> On 18/09/2015 15:19, Daniel P. Berrange wrote: > >>> + QIO_CHANNEL_FEATURE_FD_PASS = (1 << 0), > >>> + QIO_CHANNEL_FEATURE_SHUTDOWN = (1 << 1), > >>> + QIO_CHANNEL_FEATURE_DELAY = (1 << 2), > >>> + QIO_CHANNEL_FEATURE_CORK = (1 << 3), > >> > >> TCP_NODELAY and TCP_CORK are just hints; I think it is okay to just > >> ignore them if not supported. You obviously disagree, so the question > >> is why? :) > > > > Well I was just trying not to second guess what future uses we might > > have of the QIOChannel API, so I went for the approach of providing a > > way to probe any optional features upfront. Code doesn't have to use > > this if it doesn't want to - it can just ignore errors from the API > > call later. > > Perhaps we can get to a middle ground where you can probe them but no > errors are reported? > > Reporting errors is relatively heavyweight (g_new, possibly in a hot > path if the corresponding feature is not supported) and in general QEMU > never checked for the return value of socket_set_cork and > socket_set_nodelay. > > The probe, however, should also test if SOL_TCP and TCP_CORK are > defined. I think corking is a Linux-ism. Having slept on it now, I think I'll just remove these two feature flags and make the methods void with no error reporting. We can always add feature probing back at a later date if it becomes clearly required. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|