Messages in this thread |  | | From | Linus Torvalds <> | Date | Fri, 30 Nov 2012 12:37:49 -0800 | Subject | Re: [PATCH 00/10] Latest numa/core release, v18 |
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On Fri, Nov 30, 2012 at 11:58 AM, Ingo Molnar <mingo@kernel.org> wrote: > > When pushed hard enough via threaded workloads (for example via the > numa02 test) then the upstream page migration code in mm/migration.c > becomes unscalable, resulting in lot of scheduling on the anon vma > mutex and a subsequent drop in performance.
Ugh.
I wonder if migration really needs that thing to be a mutex? I may be wrong, but the anon_vma lock only protects the actual rmap chains, and migration only ever changes the pte *contents*, not the actual chains of pte's themselves, right?
So if this is a migration-specific scalability issue, then it might be possible to solve by making the mutex be a rwsem instead, and have migration only take it for reading.
Of course, I'm quite possibly wrong, and the code depends on full mutual exclusion.
Just a thought, in case it makes somebody go "Hmm.."
Linus
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