Messages in this thread | | | Date | Thu, 11 May 2006 09:53:09 -0700 | From | Ashok Raj <> | Subject | Re: [PATCH 0/10] bulk cpu removal support |
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On Wed, May 10, 2006 at 11:06:06PM -0700, Andrew Morton wrote: Hi Andrew,
> Shaohua Li <shaohua.li@intel.com> wrote: > > > > CPU hotremove will migrate tasks and redirect interrupts off dead cpu. > > This seems an awful lot of code for something which happens so infrequently. > > How big is the problem you're fixing here, and what are the > user-observeable effects of these changes?
This is useful when say a NUMA node is being removed. With new multi-core CPUs comming up, considering a 2 core with HT, we could have up to 4 logical per socket. On NUMA node with 4 sockets, a node removal will mean we do 16 single cpu offlines. Each time the process and interrupts could end up on a CPU that might be removed just immediatly.
The same is also useful for SMP Suspend/resume cases since the logical offline is same here as well.
Even thought the code changes seem a lot, most of it is just preparation of functions ready to accept a cpumask_t instead of a single cpu like earlier. The reason we split them to smaller chunks so the scope of change is well understood with each patch.
The major changes are
- stop machine to run cpu offline functions on each cpu going offline - prepare offline functions in offline path to take cpumask_t - Some task migrate dead lock removal consideration that we ran into during stress test.
I know Shaohua ran tests for more than 20+ hrs with the patch, both on i386 and x86_64.
once we get some time deltas on a bigger machine it will help a lot. Iam also trying to check with some OEM';s who have such large machines for some data.. keep posted.
ashokr
-- Cheers, Ashok Raj - Open Source Technology Center - 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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