On 02/11/2013 05:28 PM, Vincent Guittot wrote: > On 8 February 2013 19:09, Srivatsa S. Bhat > <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: >> On 02/08/2013 10:14 PM, Srivatsa S. Bhat wrote: >>> On 02/08/2013 09:11 PM, Russell King - ARM Linux wrote: >>>> On Thu, Feb 07, 2013 at 11:41:34AM +0530, Srivatsa S. Bhat wrote: >>>>> On 02/07/2013 09:44 AM, Rusty Russell wrote: >>>>>> "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> writes: >>>>>>> On 01/22/2013 01:03 PM, Srivatsa S. Bhat wrote: >>>>>>> Avg. latency of 1 CPU offline (ms) [stop-cpu/stop-m/c latency] >>>>>>> >>>>>>> # online CPUs Mainline (with stop-m/c) This patchset (no stop-m/c) >>>>>>> >>>>>>> 8 17.04 7.73 >>>>>>> >>>>>>> 16 18.05 6.44 >>>>>>> >>>>>>> 32 17.31 7.39 >>>>>>> >>>>>>> 64 32.40 9.28 >>>>>>> >>>>>>> 128 98.23 7.35 >>>>>> >>>>>> Nice! >>>>> >>>>> Thank you :-) >>>>> >>>>>> I wonder how the ARM guys feel with their quad-cpu systems... >>>>>> >>>>> >>>>> That would be definitely interesting to know :-) >>>> >>>> That depends what exactly you'd like tested (and how) and whether you'd >>>> like it to be a test-chip based quad core, or an OMAP dual-core SoC. >>>> >>> >>> The effect of stop_machine() doesn't really depend on the CPU architecture >>> used underneath or the platform. It depends only on the _number_ of >>> _logical_ CPUs used. >>> >>> And stop_machine() has 2 noticeable drawbacks: >>> 1. It makes the hotplug operation itself slow >>> 2. and it causes disruptions to the workloads running on the other >>> CPUs by hijacking the entire machine for significant amounts of time. >>> >>> In my experiments (mentioned above), I tried to measure how my patchset >>> improves (reduces) the duration of hotplug (CPU offline) itself. Which is >>> also slightly indicative of the impact it has on the rest of the system. >>> >>> But what would be nice to test, is a setup where the workloads running on >>> the rest of the system are latency-sensitive, and measure the impact of >>> CPU offline on them, with this patchset applied. That would tell us how >>> far is this useful in making CPU hotplug less disruptive on the system. >>> >>> Of course, it would be nice to also see whether we observe any reduction >>> in hotplug duration itself (point 1 above) on ARM platforms with lot >>> of CPUs. [This could potentially speed up suspend/resume, which is used >>> rather heavily on ARM platforms]. >>> >>> The benefits from this patchset over mainline (both in terms of points >>> 1 and 2 above) is expected to increase, with increasing number of CPUs in >>> the system. >>> >> >> Adding Vincent to CC, who had previously evaluated the performance and >> latency implications of CPU hotplug on ARM platforms, IIRC. >> > > Hi Srivatsa, > > I can try to run some of our stress tests on your patches. Great! > Have you > got a git tree that i can pull ? > Unfortunately, no, none at the moment.. :-( Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
