From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45570) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cvhL8-0006UI-OF for qemu-devel@nongnu.org; Wed, 05 Apr 2017 05:34:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cvhL7-0000Ij-W5 for qemu-devel@nongnu.org; Wed, 05 Apr 2017 05:34:58 -0400 Date: Wed, 5 Apr 2017 10:34:41 +0100 From: "Daniel P. Berrange" Message-ID: <20170405093441.GH21911@redhat.com> Reply-To: "Daniel P. Berrange" References: <1491384478-12325-1-git-send-email-lidongchen@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1491384478-12325-1-git-send-email-lidongchen@tencent.com> Subject: Re: [Qemu-devel] [PATCH v3] migration/block:limit the time used for block migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: jemmy858585@gmail.com Cc: qemu-devel@nongnu.org, famz@redhat.com, qemu-block@nongnu.org, quintela@redhat.com, dgilbert@redhat.com, stefanha@redhat.com, Lidong Chen On Wed, Apr 05, 2017 at 05:27:58PM +0800, jemmy858585@gmail.com wrote: > From: Lidong Chen > > when migration with high speed, mig_save_device_bulk invoke > bdrv_is_allocated too frequently, and cause vnc reponse slowly. > this patch limit the time used for bdrv_is_allocated. Can you explain why calling bdrv_is_allocated is impacting VNC performance ? Migration is running in a background thread, so shouldn't be impacting the main thread which handles VNC, unless the block layer is perhaps acquiring the global qemu lock ? I wouldn't expect such a lock to be held for just the bdrv_is_allocated call though. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|