On Fri, Nov 30, 2012 at 11:58 AM, Ingo Molnar <mi...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/