From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60468) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X30he-0001p9-Lb for qemu-devel@nongnu.org; Fri, 04 Jul 2014 06:26:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1X30hY-0005NB-Cm for qemu-devel@nongnu.org; Fri, 04 Jul 2014 06:26:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29891) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X30hY-0005N6-43 for qemu-devel@nongnu.org; Fri, 04 Jul 2014 06:26:44 -0400 Date: Fri, 4 Jul 2014 12:26:37 +0200 From: Kevin Wolf Message-ID: <20140704102637.GC4233@noname.redhat.com> References: <1404406760-22981-1-git-send-email-pbonzini@redhat.com> <53B64EE6.4000705@redhat.com> <53B6576B.7040304@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53B6576B.7040304@redhat.com> Subject: Re: [Qemu-devel] [PATCH for-2.1?!?] AioContext: speed up aio_notify List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Stefan Hajnoczi , Ming Lei , qemu-devel , Stefan Hajnoczi Am 04.07.2014 um 09:27 hat Paolo Bonzini geschrieben: > Il 04/07/2014 09:23, Ming Lei ha scritto: > >I think it is good and better to go to 2.1, and it should save lots of > >write syscall. > > > >Also should regression be caused, the per thread trick may be > >resorted to, which should be simple. > > If we have the "right" solution (which we do, unlike the plug/unplug > case), and the benefit is there but limited, I don't see a reason to > rush another patch in 2.1. > > Some reasonable level of performance degradation or increased host > CPU utilization was expected in 2.1; of course 40% is not > reasonable. > > >With multi virtqueue's coming for virtio-blk, it should save more, and I > >also plan to use the improved qemu bh to help merge requests from > >multi queue, without introducing extra notifier. > > But virtio-blk multiqueue is 2.2 material, and so is coalescing of > irqfd writes. I think Kevin or Stefan should queue this patch (with > the smp_mb optimization, IMHO) for block-next. We have a rather long freeze phase this time (which I think is a good thing). This patch fixes a regression, even if it may not be the most important one because it is in experimental code. But I still think that this time in the hard freeze is the right time to commit patches like this. I would be very hesitant with such a patch like in the two weeks before the release, but at this point I'm very open to including it. All that requiring proper review and testing, of course. I reviewed it and it looks good to me and Stefan seems to have reviewed it as well, so I think it just needs a bit more testing. Kevin