On Sun, Dec 09, 2012 at 11:17:09PM +0200, Kirill A. Shutemov wrote:

On Sun, Dec 09, 2012 at 08:36:31PM +0000, Mel Gorman 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.

Are you talking about huge zero page, right?

No, this is happening in tip/master which does not include the huge zero
page work yet. AFAIK, that's still queued in Andrew's tree for the next
merge window. It is possible that there will be collisions between numa
balancing and the huge zero page work but it hasn't happened yet.

I've fixed a race in huge zero page implementation recently[1]. Symptoms
were similar -- SIGSEGV in JVM. The patch is in mmotm-2012-12-05-16-56 and
later.

It might be a similar class of bug.

-- 
Mel Gorman
SUSE Labs

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