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Date: Fri, 9 Apr 2021 07:26:38 -0700 From: Doug Smythies <dsmythies@...us.net> To: Pratik Sampat <psampat@...ux.ibm.com> Cc: rjw@...ysocki.net, Daniel Lezcano <daniel.lezcano@...aro.org>, shuah@...nel.org, ego@...ux.vnet.ibm.com, svaidy@...ux.ibm.com, Linux PM list <linux-pm@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-kselftest@...r.kernel.org, pratik.r.sampat@...il.com, dsmythies <dsmythies@...us.net> Subject: Re: [RFC v3 0/2] CPU-Idle latency selftest framework On Fri, Apr 9, 2021 at 12:43 AM Pratik Sampat <psampat@...ux.ibm.com> wrote: > On 09/04/21 10:53 am, Doug Smythies wrote: > > I tried V3 on a Intel i5-10600K processor with 6 cores and 12 CPUs. > > The core to cpu mappings are: > > core 0 has cpus 0 and 6 > > core 1 has cpus 1 and 7 > > core 2 has cpus 2 and 8 > > core 3 has cpus 3 and 9 > > core 4 has cpus 4 and 10 > > core 5 has cpus 5 and 11 > > > > By default, it will test CPUs 0,2,4,6,10 on cores 0,2,4,0,2,4. > > wouldn't it make more sense to test each core once? > > Ideally it would be better to run on all the CPUs, however on larger systems > that I'm testing on with hundreds of cores and a high a thread count, the > execution time increases while not particularly bringing any additional > information to the table. > > That is why it made sense only run on one of the threads of each core to make > the experiment faster while preserving accuracy. > > To handle various thread topologies it maybe worthwhile if we parse > /sys/devices/system/cpu/cpuX/topology/thread_siblings_list for each core and > use this information to run only once per physical core, rather than > assuming the topology. > > What are your thoughts on a mechanism like this? Yes, seems like a good solution. ... Doug
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