Messages in this thread | | | Date | Thu, 13 Mar 2008 08:14:13 -0700 | From | Greg KH <> | Subject | Re: hackbench regression since 2.6.25-rc |
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On Thu, Mar 13, 2008 at 03:46:57PM +0800, Zhang, Yanmin 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.
Where is the kernel panicing? The changeset right after the last one above: bc87d2fe7a1190f1c257af8a91fc490b1ee35954, is a change to efivars, are you using that in your .config?
> All patches between the 2 tags are on kobject restructure. I guess such restructure > creates more cache miss on the 16-core tigerton.
Nothing should be creating kobjects on a normal load like this, so a regression seems very odd. Unless the /sys/kernel/uids/ stuff is triggering this?
Do you have a link to where I can get hackbench (google seems to find lots of reports with it, but not the source itself), so I can test to see if we are accidentally creating kobjects with this load?
thanks,
greg k-h
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