Hi Srivatsa, I can try to run some of our stress tests on your patches. Have you got a git tree that i can pull ? Regards, Vincent 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. > > 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
