Messages in this thread | | | Date | Sat, 13 Nov 2010 17:15:10 -0800 | Subject | Re: divide error in select_task_rq_fair() | From | Yinghai Lu <> |
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On Thu, Nov 11, 2010 at 10:28 AM, Myron Stowe <myron.stowe@hp.com> wrote: > On Fri, 2010-11-05 at 07:17 +0100, Eric Dumazet wrote: >> Le jeudi 04 novembre 2010 à 20:00 -0600, Bjorn Helgaas a écrit : >> >> > Is that going to help you debug the problem? The solution is not going >> > to be something like "set NR_CPUS=x". If NR_CPUS is too small, the >> > machine should still *boot*, even if we can't use all the CPUs in the >> > box. >> > >> >> Yes, it will help to understand the layout of cpu / domains and make >> appropriate changes. >> >> Alternative is you send me such a machine :=) > > I opened a BZ on this issue as it seems to be a regression - > https://bugzilla.kernel.org/show_bug.cgi?id=22662 > > I also, as indicated in the BZ, bisected the kernel which gave the > following results and reverting 50f2d7f682f9c0ed58191d0982fe77888d59d162 > did re-enable booting on the box in question (an HP dl980g7). Let me > know what further info you need or patches to test for debugging this. > > Thanks, > > commit 50f2d7f682f9c0ed58191d0982fe77888d59d162 > Author: Nikanth Karthikesan <knikanth@suse.de> > Date: Thu Sep 30 17:34:10 2010 +0530 > > x86, numa: Assign CPUs to nodes in round-robin manner on fake NUMA > > commit d9c2d5ac6af87b4491bff107113aaf16f6c2b2d9 "x86, numa: Use near(er) > online node instead of roundrobin for NUMA" changed NUMA initialization on > Intel to choose the nearest online node or first node. Fake NUMA would be > better of with round-robin initialization, instead of the all CPUS on > first node. Change the choice of first node, back to round-robin. > > For testing NUMA kernel behaviour without cpusets and NUMA aware > applications, it would be better to have cpus in different nodes, rather > than all in a single node. With cpusets migration of tasks scenarios > cannot not be tested. > > I guess having it round-robin shouldn't affect the use cases for all cpus > on the first node. > > The code comments in arch/x86/mm/numa_64.c:759 indicate that this used to > be the case, which was changed by commit d9c2d5ac6. It changed from > roundrobin to nearer or first node. And I couldn't find any reason for > this change in its changelog. > > Signed-off-by: Nikanth Karthikesan <knikanth@suse.de> > Cc: David Rientjes <rientjes@google.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
please check
http://lkml.org/lkml/2010/11/13/176
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