Messages in this thread | | | Subject | hackbench [pthread mode] regression with 2.6.29-rc3 | From | "Zhang, Yanmin" <> | Date | Sun, 01 Feb 2009 15:30:26 +0800 |
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Comparing with 2.6.29-rc2's result, hackbench [pthread mode] result is increased about 50%~100% with 2.6.29-rc3 on my 4 qual-core process tigerton machine and 4 qual-core Montvale Itanium mahchine. The smaller result, the better performance. Command to run hackbench: #./hackbench 100 thread 2000
Bisect located below patch. commit 490dea45d00f01847ebebd007685d564aaf2cd98 Author: Peter Zijlstra <peterz@infradead.org> Date: Mon Nov 24 17:06:57 2008 +0100
itimers: remove the per-cpu-ish-ness
Either we bounce once cacheline per cpu per tick, yielding n^2 bounces or we just bounce a single..
Also, using per-cpu allocations for the thread-groups complicates the per-cpu allocator in that its currently aimed to be a fixed sized allocator and the only possible extention to that would be vmap based, which is seriously constrained on 32 bit archs.
After above patch is reverted, hackbench result is restored.
yanmin
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