Messages in this thread | | | Subject | Re: Information for setting up SMT related parameters on linux 2.6.16 on POWER5 | From | Will Schmidt <> | Date | Mon, 08 May 2006 15:03:38 -0500 |
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On Mon, 2006-05-08 at 12:09 -0600, Meswani, Mitesh wrote: > > Hello
Hi
> > I am looking to use the SMT related parameters like Snooze delay, HMT > thread priorities, SMT ON/Off and wanted to know how to invoke and set > them. I am running Open Suse 10 with 2.6.16.rc4-3-ppc64 kernel on > eServer p590 2-way POWER5 partition.
> > I noticed the parameters in /sys/devices/system/cpu/cpu# with the > following : > > mmcr0 online pmc2 pmc5 smt_snooze_delay > mmcr1 physical_id pmc3 pmc6 topology > crash_notes mmcra pmc1 pmc4 purr >
Some of this is unique to Logical Partitions and cpu's on POWER5 pSeries hardware.. I think you've already found the useful entry "online", and the rest would be just trivial information.
On the kernel boot commandline, you can add parms such as "smt-snooze-delay=xxxx" to set the snooze_delay value, and "smt-enabled=off" to turn off the secondary threads.
As you've already found, you can echo values into the sys entries to cause the cpus to go online or offline. 0=offline, 1=online. You can also adjust the value for snooze-delay. This one defaults to '0'. This controls the amount of time the processor thread spins before declaring that it's got no useful work to do and cedes itself.
"mmcr*" and "pmc*" are performance counter registers and values. These are used by oprofile.
"purr" is a Processor Utilization Resource Register, indicating the number of ticks that the processor has been in use.
I believe "crash_notes" has to do with lkcd or crashdump.
No idea on the "topology" entry. possibly related to NUMA.
> setting the value in online to 0 seems to turn off the logical > processor, but I am not sure what the others are for and the meaning > of their hex values? > It seems that there is include/asm-ppc64/processor.h with macros like > HMT_very_low() , wonder if these can be set on command line > since I am running unmodified app binaries.
the HMT_* macros are telling firmware that "this processor thread should run at this priority". Typically used when we're waiting on a spinlock. I.e. When we are waiting on a spinlock, we hit the HMT_low macro to drop our threads priority, allowing the other thread to use those extra cycles finish it's stuff quicker, and maybe even release the lock we're waiting for. HMT_* is all within the kernel though, no exposure to userspace apps.
> > Thanks, > Mitesh > >
Hope that is helpful.. -Will
> Mitesh R. Meswani > Ph.D. Candidate > Research Associate, PLS2 Group > Room 106 F, Department of Computer Science > The University of Texas at El Paso, > El Paso, Texas 79968 > Tel: 915 747 8012 (O) > Email: mmeswani@utep.edu > > ______________________________________________________________________ > From: linuxppc-dev-bounces+mmeswani=utep.edu@ozlabs.org on behalf of > Geoff Levand > Sent: Fri 5/5/2006 6:00 PM > To: Paul Mackerras > Cc: Arnd Bergmann; Levand,Geoffrey; linux-kernel@vger.kernel.org; > linuxppc-dev@ozlabs.org; Arnd Bergmann; cbe-oss-dev@ozlabs.org > Subject: Re: [PATCH 04/13] cell: remove broken __setup_cpu_be function > <Snippage...>
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