From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [PATCHv3 4/6] evtchn: use a per-event channel lock for sending events Date: Thu, 18 Jun 2015 12:20:12 +0100 Message-ID: <5582C58C020000780008692C@mail.emea.novell.com> References: <1434542583-28073-1-git-send-email-david.vrabel@citrix.com> <1434542583-28073-5-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Z5Xrm-0000t3-Q7 for xen-devel@lists.xenproject.org; Thu, 18 Jun 2015 11:20:18 +0000 In-Reply-To: <1434542583-28073-5-git-send-email-david.vrabel@citrix.com> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: David Vrabel Cc: xen-devel@lists.xenproject.org, Keir Fraser , Ian Campbell , Tim Deegan List-Id: xen-devel@lists.xenproject.org >>> On 17.06.15 at 14:03, wrote: > When sending an event, use a new per-event channel lock to safely > validate the event channel state. > > This new lock must be held when changing event channel state. Note > that the event channel lock must also be held when changing state from > ECS_FREE or it will race with a concurrent get_free_port() call. > > To avoid having to take the remote event channel locks when sending to > an interdomain event channel, the local and remote channel locks are > both held when binding or closing an interdomain event channel. > > This significantly increases the number of events that can be sent > from multiple VCPUs. But struct evtchn increases in size, reducing > the number that fit into a single page to 64 (instead of 128). > > Signed-off-by: David Vrabel Reviewed-by: Jan Beulich But iiuc this functionally depends on the earlier patches, and hence can't go in without the issues there addressed. Jan