Messages in this thread | | | Date | Fri, 19 Mar 2004 20:14:50 -0800 | From | Andrew Morton <> | Subject | Re: 2.6.4-mm2 |
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Nick Piggin <piggin@cyberone.com.au> wrote: > > >>> > >>Thanks, so it's the CPU scheduler changes. Is that machine hyperthreaded? > >>And do you have CONFIG_X86_HT enabled? > >> > > > >Yes and CONFIG_X86_HT is enabled but I have hyperthreading disabled with > >'acpi=off noht' (whichever one does it.) > > > > > The oprofile for the 01 kernel says > CPU: P4 / Xeon, speed 1497.76 MHz (estimated) > while the 02 kernel says > CPU: P4 / Xeon with 2 hyper-threads, speed 1497.57 MHz (estimated) > What's going on there?
Does the sched-domains patch break `acpi=off' or `noht'?
> Other than that, nothing in the kernel profile jumps out at me: > schedule, __copy_from_user_ll and __copy_to_user_ll are all > significantly lower *after* the CPU scheduler changes, which > is an indicator that cache behaviour is better.
No, it indicates that the kernel is getting less work done.
> Sar says average context switches/second were 9064 and 6567 before > and after. > > The only thing I can see is the CPU utilisation averages show the > scheduler patches have more of a tendancy to load up one CPU more > before moving to another. This actually should be good behaviour, > generally but I wonder if it is hurting at all. I would be really > surprised if it was that significant.
This machine is I/O-bound, the CPUs are mostly idle. It would appear to be some interaction between the I/O system and the CPU scheduler. Haven't we seen that with reaim also?
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