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Message-ID: <20120723211206.GZ9222@suse.de> Date: Mon, 23 Jul 2012 22:12:06 +0100 From: Mel Gorman <mgorman@...e.de> To: linux-mm@...ck.org Cc: linux-kernel@...r.kernel.org Subject: [MMTests] Scheduler Configuration: global-dhp__scheduler-performance Result: http://www.csn.ul.ie/~mel/postings/mmtests-20120424/global-dhp__scheduler-performance Benchmarks: hackbench-pipes hackbench-sockets pipetest starve lmbench Summary ======= This is a mixed bag. The results on an I7 generally look great! There are some major improvemnets in there and I think this may be due to scheduler developers working with the latest chips. The other machines did not far as well. Look at pipetest on hydra for an example of a particularly bad set of results. Benchmark notes =============== starve (http://www.hpl.hp.com/research/linux/kernel/o1-starve.php) was chosen because even though it is designed to isolate a bug in the O(1) scheduler, it is still interesting to monitor for performance regressions. It does not take any special parameters. hackbench was chosen because it's a general scheduler benchmark that is sensitive to regressions in the scheduler fast-path. It is difficult to draw conclusions from as it is somewhat sensitive to the starting conditions of the machine but trends over time may be observed. It is run in both pipe and sockets mode and for each number of clients, it is run for 30 iterations. pipetest is a scheduler ping-pong test that measures context switch latency. It runs for 30 iterations. lmbench is just running the lat_ctx test and is another measure of context switch latency. =========================================================== Machine: arnold Result: http://www.csn.ul.ie/~mel/postings/mmtests-20120424/global-dhp__scheduler-performance/arnold/comparison.html Arch: x86 CPUs: 1 socket, 2 threads Model: Pentium 4 Disk: Single Rotary Disk Status: Context switch latency is regressing. =========================================================== starve is looking ok except for 3.0 and 3.1 where System CPU time and elapsed time increased. This was fixed in later kernels but worth noting for users of -stable. lmbench showed a small regression in 3.0 where context switch latency was increased and this has not been recovered yet. 3.3.6 was particularly bad for low numbers of clients. hackbench-pipes looks ok in comparison to 2.6.32. The "Time ratio" graph shows that kernels are below the red line reflecting that most kernels are faster. However, it also shows that 2.6.34 was the "best" kernel and recent kernels have regressed slightly hackbench-sockets regressed badly after 2.6.34 until 3.3 which should be investigated. Again this is most obvious in the Time Ratio graph pipetest is showing major regressions in latency since some time between 2.6.34 and 2.6.39. ========================================================== Machine: hydra Result: http://www.csn.ul.ie/~mel/postings/mmtests-20120424/global-dhp__scheduler-performance/hydra/comparison.html Arch: x86-64 CPUs: 1 socket, 4 threads Model: AMD Phenom II X4 940 Disk: Single Rotary Disk Status: pipetest is particularly bad. ========================================================== starve is generally ok although again, 3.0 and 3.1 both regressed on System CPU time. This was improved on kernels after that but it's still a little worse than 2.6.32 was. lmbench shows no regression in 3.0 unlike on arnold but later kernels are much worse with the latency of 3.4 being generally higher than it was in 3.2 hackbench-pipes generally looks ok. hackbench-sockets is generally bad. 3.1 was particularly bad and while 3.4 has improved the situation a bit, it is still worse than 2.6.32. pipetest is showing major regressions. 3.2 regressed particularly badly. ========================================================== Machine: sandy Result: http://www.csn.ul.ie/~mel/postings/mmtests-20120424/global-dhp__scheduler-performance/sandy/comparison.html Arch: x86-64 CPUs: 1 socket, 8 threads Model: Intel Core i7-2600 Disk: Single Rotary Disk Status: Generally great. ========================================================== starve is generally ok. 3.0 regressed in terms of System CPU time but recent kernels are very good. This might reflect that a lot of people are testing with later Intel processors to the detriment of older models. lmbench is looking superb. hackbench-pipes looks great. hackbench-sockets does not look as great but it's still very good. pipetest is generally looking good in comparison to 2.6.32. However, I am concerned that 3.4 is worse than 3.3. -- Mel Gorman SUSE Labs -- 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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