Messages in this thread | | | Date | Tue, 25 Feb 2020 11:44:38 +0800 | From | Aaron Lu <> | Subject | Re: [RFC PATCH v4 00/19] Core scheduling v4 |
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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.
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