Messages in this thread Patch in this message | | | From | Nikanth Karthikesan <> | Subject | Re: divide error in select_task_rq_fair() | Date | Fri, 12 Nov 2010 11:52:29 +0530 |
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On Thursday 11 November 2010 23:58:04 Myron Stowe 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> > > > Thanks >
Can you try with this patch?
Thanks Nikanth
Fallback to first node, if the node is not online.
Fixes regression of commit 50f2d7f682f9c0ed58191d0982fe77888d59d162 x86, numa: Assign CPUs to nodes in round-robin manner on fake NUMA
When some of the NUMA nodes are disabled, and the CPUs are assigned in round-robin fashion, CPUs might be assigned to disabled nodes resulting in the crash. While using round-robin assignment, check if the node is online. If the node is not online, use the first online node.
Reported-by: Bjorn Helgaas <bjorn.helgaas@hp.com> Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
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diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index d16c2c5..f31237c 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -287,6 +287,8 @@ static void __cpuinit srat_detect_node(struct cpuinfo_x86 *c) if (node == NUMA_NO_NODE || !node_online(node)) { /* reuse the value from init_cpu_to_node() */ node = cpu_to_node(cpu); + if (!node_online(node)) + node = first_node(node_online_map); } numa_set_node(cpu, node); #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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