Messages in this thread | | | Date | Thu, 6 Jul 2006 17:01:51 -0700 | From | Paul Jackson <> | Subject | Re: [PATCH 2.6.16-mm1 2/2] sched_domains: Allocate sched_groups dynamically |
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Several months ago, Srivatsa wrote: > I couldn't test this on a multi-core machine, since I don't think we > have one in our lab. > > Suresh, would you mind testing the patch on a multi-core machine, in case you > have access to one? > > Basically you would need to do create a exclusive CPUset with one CPU in it > (ensure that its sibling in the same core is not part of the same > CPUset). As soon as you make the CPUset exclusive, you would hit some > kind of hang. With this patch, the hang should go away.
Summary: Where do we stand with multi-core and this bug?
I don't see a reply from Suresh on whether he could test on multi-core.
I finally happened to be running on a hyper-threaded box last week, and stumbled over this bug that Srivatsa's patch fixes. Hawkes remembered Srivatsa's patch, I tried it, and it worked. Thanks!
But now I'm quite confused as to the situation with multi-core.
Details of my confusions, for the bored:
From Srivatsa's remark, I would have guessed that multi-core was at risk for this bug too, but Srivatsa was hopeful that his patch would fix that too.
Early this week, a couple of people who shall remain anonymous here raised the question of whether we had the same problem with multi-core. One of them believed that multi-core did have the same problem.
I got a little time on a multi-core system this morning to test it, and while running what I -thought- was a kernel -without- Srivatsa's patch, I could not find any problem. I made a cpuset with just a single logical cpu in it, and marked it cpu_exclusive, and the system did not hang.
It will be another day before I can get on that multi-core system again to verify my findings.
I was hoping that someone could actually -read- this code and state with confidence that one of the following held: * it was already working ok on multi-core (a one CPU cpu_exclusive cpuset), * it was broken, but Srivatsa's patch fixes it, or * it's still broken, even with Srivatsa's patch.
I tried a couple of times to read the code myself, but could not make any headway there.
So ... what's up with multi-core and this bug?
-- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson <pj@sgi.com> 1.925.600.0401 - 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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