Re: hackbench regression with 2.6.26-rc2 on tulsa machine
From: Mike Galbraith
Date: Tue May 20 2008 - 05:22:44 EST
On Tue, 2008-05-20 at 16:09 +0800, Zhang, Yanmin wrote:
> Comparing with 2.6.26-rc1, hackbench has about 30% regression with 2.6.26-rc2 on my tulsa machine
> which is a netburst architecure hyper-threading x86_64.
> Command line to test: #hackbench 100 process 2000
> With ï2.6.26-rc1, it takes 30 seconds. But with 2.6.26-rc2/rc3, it takes 40 seconds.
> Bisect located below patch:
> 46151122e0a2e80e5a6b2889f595e371fe2b600d is first bad commit
> commit 46151122e0a2e80e5a6b2889f595e371fe2b600d
> Author: Mike Galbraith <efault@xxxxxx>
> Date: Thu May 8 17:00:42 2008 +0200
> sched: fix weight calculations
> The conversion between virtual and real time is as follows:
> dvt = rw/w * dt <=> dt = w/rw * dvt
> Since we want the fair sleeper granularity to be in real time, we actually
> need to do:
> dvt = - rw/w * l
> The bisect steps look stable.
> On my core architecure machines(stoakley and tigerton), I do see improvement instead of regression,
> like result from 31 seconds down to 28 seconds.
> I'm not sure if hyper-threading need more cares in this situation.
Oh joy. I'll update my poor old P4 and see what I can duplicate this.
Do you still have group scheduling enabled? If so, can you turn it off
and try again? (when in doubt, grasp at any straw within reach;)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/