Messages in this thread | | | From | Aubrey Li <> | Date | Tue, 25 Feb 2020 13:32:35 +0800 | Subject | Re: [RFC PATCH v4 00/19] Core scheduling v4 |
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On Tue, Feb 25, 2020 at 11:44 AM Aaron Lu <aaron.lwe@gmail.com> wrote: > > On Fri, Feb 14, 2020 at 02:10:53PM +0800, Aubrey Li wrote: > > On Fri, Feb 14, 2020 at 2:37 AM Tim Chen <tim.c.chen@linux.intel.com> wrote: > > > > > > On 2/12/20 3:07 PM, Julien Desfossez wrote: > > > > > > >> > > > >> Have you guys been able to make progress on the issues with I/O intensive workload? > > > > > > > > I finally have some results with the following branch: > > > > https://github.com/digitalocean/linux-coresched/tree/coresched/v4-v5.5.y > > > > > > > > > > > > So the main conclusion is that for all the test cases we have studied, > > > > core scheduling performs better than nosmt ! This is different than what > > > > we tested a while back, so it's looking really good ! > > > > > > Thanks for the data. They look really encouraging. > > > > > > Aubrey is working on updating his patches so it will load balance > > > to the idle cores a bit better. We are testing those and will post > > > the update soon. > > > > I added a helper to check task and cpu cookie match, including the > > entire core idle case. The refined patchset updated at here: > > https://github.com/aubreyli/linux/tree/coresched_v4-v5.5.2 > > > > This branch also includes Tim's patchset. According to our testing > > result, the performance data looks on par with the previous version. > > A good news is, v5.4.y stability issue on our 8 numa node machine > > is gone on this v5.5.2 branch. > > One problem I have when testing this branch: the weight of the croup > seems to be ignored. > > On a 2sockets/16cores/32threads VM, I grouped 8 sysbench(cpu mode) > threads into one cgroup(cgA) and another 16 sysbench(cpu mode) threads > into another cgroup(cgB). cgA and cgB's cpusets are set to the same > socket's 8 cores/16 CPUs and cgA's cpu.shares is set to 10240 while cgB's > cpu.shares is set to 2(so consider cgB as noise workload and cgA as > the real workload). > > I had expected cgA to occupy 8 cpus(with each cpu on a different core) > most of the time since it has way more weight than cgB, while cgB should > occupy almost no CPUs since: > - when cgB's task is in the same CPU queue as cgA's task, then cgB's > task is given very little CPU due to its small weight; > - when cgB's task is in a CPU queue whose sibling's queue has cgA's > task, cgB's task should be forced idle(again, due to its small weight). > > But testing shows cgA occupies only 2 cpus during the entire run while > cgB enjoys the remaining 14 cpus. As a comparison, when coresched is off, > cgA can occupy 8 cpus during its run. > > I haven't taken a look at the patches, but would like to raise the > problem first. My gut feeling is that, we didn't make the CPU's load > balanced. > > P.S. it's not that I care about VM's performance, it's just easier to > test kernel stuff using a VM than on a bare metal. Its CPU setup might > seem weird, I just set it up to be the same as my host setup.
Aaron - did you test this before? In other words, if you reset repo to your last commit:
- 5bd3c80 sched/fair : Wake up forced idle siblings if needed
Does the problem remain? Just want to check if this is a regression introduced by the subsequent patchset.
Thanks, -Aubrey
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