hi Srikar,

* Srikar Dronamraju [off-list ref] wrote:

quoted

Either way, last night I applied a patch on top of latest tip/master to
remove the nr_cpus_allowed check so that numacore would be enabled again
and tested that. In some places it has indeed much improved. In others
it is still regressing badly and in two case, it's corrupting memory --
specjbb when THP is enabled crashes when running for single or multiple
JVMs. It is likely that a zero page is being inserted due to a race with
migration and causes the JVM to throw a null pointer exception. Here is
the comparison on the rough off-chance you actually read it this time.

I see this failure when running with THP and KSM enabled on 
Friday's Tip master. Not sure if Mel was talking about the same issue.

------------[ cut here ]------------
kernel BUG at ../kernel/sched/fair.c:2371!

Could you check whether today's -tip (7ea8701a1a51 or later), 
plus the patch below, addresses the crash - while still giving 
good NUMA performance?

Thanks,

	Ingo

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9d11a8a..6a89787 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c

@@ -2351,6 +2351,9 @@ void task_numa_fault(unsigned long addr, int node, int last_cpupid, int pages, b
 	int priv;
 	int idx;
 
+	if (!p->numa_faults)
+		return;
+
 	if (last_cpupid != cpu_pid_to_cpupid(-1, -1)) {
 		/* Did we access it last time around? */
 		if (last_pid == this_pid) {

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