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Date: Wed, 20 Jan 2010 07:51:41 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Clark Williams <williams@...hat.com> cc: RT <linux-rt-users@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Carsten Emde <ce@...g.ch>, John Kacur <jkacur@...hat.com> Subject: Re: RFC: NUMA modifications to cyclictest On Tue, 19 Jan 2010, Clark Williams wrote: > RT-ers, > > Lately we've been struggling with some performance issues on high-core > count (>16 cores) NUMA machines with the RT kernel. During the course > of troubleshooting this issue, we tried using the 'numactl' program to > constrain our measurement testing tool (rteval) to a particular memory > node, rather than letting everything float. Doing so showed marked > improvement in both max latency and jitter. While this doesn't solve > our performance problems I thought it might make sense to have a --numa > mode for cylictest that compliments the --smp mode just added. > > The big difference here is that when using --numa, each measurement > thread (one per cpu) has it's stack allocated from the memory node > associated with it's cpu. Also, the major data structures for each > thread (parameter block, statistics block and histogram) are allocated > from the appropriate node. This is done with calls into libnuma, > which means this will add a dependency on libnuma. That might cause some trouble for embedded folks. :( > The intent is to measure latency on a numa system in the same way a > well-written RT application would run on a NUMA machine, that is > minimizing the off-node memory references. Agreed. tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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