Messages in this thread |  | | | Subject | Re: Scalability requirements for sysv ipc | | From | Peter Zijlstra <> | | Date | Tue, 25 Mar 2008 17:13:50 +0100 |
On Tue, 2008-03-25 at 16:50 +0100, Mike Galbraith wrote: > On Sat, 2008-03-22 at 20:08 +0100, Manfred Spraul wrote: > > > just the normal performance of 2.6.25-rc3 is abyssimal, 55 to 60% slower > > than 2.6.18.8: > > After manually reverting 3e148c79938aa39035669c1cfa3ff60722134535, > 2.6.25.git scaled linearly, but as you noted, markedly down from earlier > kernels with this benchmark. 2.6.24.4 with same revert, but all > 2.6.25.git ipc changes piled on top still performed close to 2.6.22, so > I went looking. Bisection led me to.. > > 8f4d37ec073c17e2d4aa8851df5837d798606d6f is first bad commit > commit 8f4d37ec073c17e2d4aa8851df5837d798606d6f > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Fri Jan 25 21:08:29 2008 +0100 > > sched: high-res preemption tick > > Use HR-timers (when available) to deliver an accurate preemption tick. > > The regular scheduler tick that runs at 1/HZ can be too coarse when nice > level are used. The fairness system will still keep the cpu utilisation 'fair' > by then delaying the task that got an excessive amount of CPU time but try to > minimize this by delivering preemption points spot-on. > > The average frequency of this extra interrupt is sched_latency / nr_latency. > Which need not be higher than 1/HZ, its just that the distribution within the > sched_latency period is important. > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > Signed-off-by: Ingo Molnar <mingo@elte.hu> > > :040000 040000 ab225228500f7a19d5ad20ca12ca3fc8ff5f5ad1 f1742e1d225a72aecea9d6961ed989b5943d31d8 M arch > :040000 040000 25d85e4ef7a71b0cc76801a2526ebeb4dce180fe ae61510186b4fad708ef0211ac169decba16d4e5 M include > :040000 040000 9247cec7dd506c648ac027c17e5a07145aa41b26 950832cc1dc4d30923f593ecec883a06b45d62e9 M kernel > > ...and I verified it via :-/ echo 7 > sched_features in latest. That > only bought me roughly half though, so there's a part three in there > somewhere.
Ouch, I guess hrtimers are just way expensive on some hardware...
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