Messages in this thread |  | | | Date | Thu, 13 Mar 2008 01:48:08 -0700 | | From | Andrew Morton <> | | Subject | Re: hackbench regression since 2.6.25-rc |
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On Thu, 13 Mar 2008 15:46:57 +0800 "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> wrote:
> Comparing with 2.6.24, on my 16-core tigerton, hackbench process mode has about > 40% regression with 2.6.25-rc1, and more than 20% regression with kernel > 2.6.25-rc4, because rc4 includes the reverting patch of scheduler load balance. > > Command to start it. > #hackbench 100 process 2000 > I ran it for 3 times and sum the values. > > I tried to investiagte it by bisect. > Kernel up to tag 0f4dafc0563c6c49e17fe14b3f5f356e4c4b8806 has the 20% regression. > Kernel up to tag 6e90aa972dda8ef86155eefcdbdc8d34165b9f39 hasn't regression. > > Any bisect between above 2 tags cause kernel hang. I tried to checkout to a point between > these 2 tags for many times manually and kernel always paniced. > > All patches between the 2 tags are on kobject restructure. I guess such restructure > creates more cache miss on the 16-core tigerton. >
That's pretty surprising - hackbench spends most of its time in userspace and zeroing out anonymous pages. It shouldn't be fiddling with kobjects much at all.
Some kernel profiling might be needed here..
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