From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: Is patches/linux-2.6.18/xen-hotplug.patch still necessary? Date: Wed, 09 May 2007 09:38:00 -0600 Message-ID: <1178725080.6512.6.camel@lappy> References: Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: xen-devel List-Id: xen-devel@lists.xenproject.org On Wed, 2007-05-09 at 16:32 +0100, Keir Fraser wrote: > On 9/5/07 16:07, "Alex Williamson" wrote: > > >> It has to be handled in top itself. With some versions at least it was the > >> case that top would crash when CPUs where hot-unplugged. If you revert that > >> patch, does your version of top work okay in the hot-unplug case (you have > >> to run top across the unplug operation to see if it will crash or not)? > > > > Top still crashes without that patch, but the patch just hides the > > problem. Top also crashes during a CPU hotplug operation on bare metal. > > I think this patch causes more problems than if fixes. Thanks, > > The fact that physical CPU hotplug is an incredibly rare operation, even on > the 0.001% of all systems that it is actually supported on, compared with > virtual CPU hotplug being potentially quite frequent, is a real concern. > Users are actually moderately likely to see this bug when running on Xen. In > fact they used to, and then they complained to us, at which point we applied > the band-aid solution. Likewise, I've had users complain that the sysconf(_SC_NPROCESSORS_ONLN) fails to report the correct number of online CPUs with this patch. Thanks, Alex -- Alex Williamson HP Open Source & Linux Org.