Messages in this thread | | | Subject | Re: volano ~30% regression with 2.6.33-rc1 & -rc2 | From | Peter Zijlstra <> | Date | Mon, 04 Jan 2010 14:26:48 +0100 |
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On Mon, 2010-01-04 at 14:15 +0100, Mike Galbraith wrote: > On Mon, 2010-01-04 at 14:02 +0100, Peter Zijlstra wrote: > > On Mon, 2010-01-04 at 13:57 +0100, Mike Galbraith wrote: > > > On Mon, 2010-01-04 at 04:40 -0800, Arjan van de Ven wrote: > > > > On Mon, 04 Jan 2010 16:15:58 +0800 > > > > Lin Ming <ming.m.lin@intel.com> wrote: > > > > > > > > > Mike & Peter, > > > > > > > > > > Compared with 2.6.32, volano has ~30% regression with 2.6.33-rc1 & > > > > > -rc2. Testing machine: Tigerton Xeon, 16cpus(4P/4Core), 16G memory > > > > > > > > did this show up only on this cpu? > > > > (since this is a multi-core-without-shared-cache cpu, it could be that > > > > we get the topology wrong and think cores share cache where they don't) > > > > > > My fault for using PREFER_SIBLING I guess. However, I do wonder why in > > > the heck we set that at the CPU domain level. Siblings lie northward. > > > > Ah, PREFER_SIBLING means prefer sibling domain, not sibling thread. Its > > set at the CPU (really socket) level so make tasks spread over sockets > > first, so that there is no competition for the socket wide resources. > > WRT the regression, would you prefer only the sched_fair.c hunk, and > maybe plunking the topology hunk in sched_devel, or both lines in one > patch, since ramp-up gain remains unrealized half of the time on Nehalem > and ilk.
Both bits seem sane I guess, you change SD_SIBLING_INIT(), right? Threads really do share package resources so it makes sense to set it.
I guess its back to poking at nehalem to see what makes it tick..
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