From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: RFC: mem_event: use wait queue when ring is full Date: Wed, 23 Nov 2011 17:17:24 +0000 Message-ID: References: <20111123164918.GB6000@aepfle.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20111123164918.GB6000@aepfle.de> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Olaf Hering , Andres Lagar-Cavilla Cc: xen-devel@lists.xensource.com, adin@gridncetric.ca List-Id: xen-devel@lists.xenproject.org On 23/11/2011 16:49, "Olaf Hering" wrote: > On Tue, Nov 22, Andres Lagar-Cavilla wrote: > >> Olaf, two questions here >> >> - do you have any insight for events caused by foreign mappings? Those >> will be lost with a full ring, with or without wait queues > > The callers of mem_event_check_ring() have to retry if the ring is full. > Thats what happens with p2m_mem_paging_populate(), the callers return > -ENOENT and expect a retry at some later point. > >> - we have posted a patch (twice) previously, with changes to ring >> management, most importantly sending guest vcpus to sleep when space in >> the ring is < d->max_vcpus. I see these two patches as complementary. What >> is your take? > > I'm not proposing to include my patch as is, because it has one issue: > wake_up will start all waiting vcpus even if there is just a single slot > free in the ringbuffer. You patch is better in this respect because only > a few will be started again. Do you need a wake_up_one() function? -- Keir > I will send comments for it later. > > Olaf > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel