Messages in this thread | | | Date | Thu, 27 Feb 2020 09:10:33 -0500 | From | Phil Auld <> | Subject | Re: [RFC PATCH v4 00/19] Core scheduling v4 |
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Hi Aaron,
On Thu, Feb 27, 2020 at 10:04:32AM +0800 Aaron Lu wrote: > On Tue, Feb 25, 2020 at 03:51:37PM -0500, Vineeth Remanan Pillai wrote: > > 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) > > > > The expected behaviour could also be that 8 processes share 4 cores and > > 8 hw threads right? This is what we are seeing mostly > > I expect the 8 cgA tasks to spread on each core, instead of occupying > 4 cores/8 hw threads. If they stay on 4 cores/8 hw threads, than on the > core level, these cores' load would be much higher than other cores > which are running cgB's tasks, this doesn't look right to me. >
I don't think that's a valid assumption, at least since the load balancer rework.
The scheduler will be looking much more at the number of running task versus the group weight. So in this case 2 running tasks, 2 siblings at the core level will look fine. There will be no reason to migrate.
> I think the end result should be: each core has two tasks queued, one > cgA task and one cgB task(to maintain load balance on the core level). > The two tasks are queued on different hw thread, with cgA's task runs > most of the time on one thread and cgB's task being forced idle most > of the time on the other thread. >
With the core scheduler that does not seem to be a desired outcome. I think grouping the 8 cgA tasks on the 8 cpus of 4 cores seems right.
Cheers, Phil
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