Messages in this thread | | | Date | Wed, 24 Oct 2018 12:21:53 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH v2] sched/core: Don't mix isolcpus and housekeeping CPUs |
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On Wed, Oct 24, 2018 at 04:11:24PM +0530, Srikar Dronamraju wrote: > * Peter Zijlstra <peterz@infradead.org> [2018-10-24 12:15:08]: > > > On Wed, Oct 24, 2018 at 03:16:46PM +0530, Srikar Dronamraju wrote: > > > * Mel Gorman <mgorman@techsingularity.net> [2018-10-24 09:56:36]: > > > > > > > On Wed, Oct 24, 2018 at 08:32:49AM +0530, Srikar Dronamraju wrote: > > > > It would certainly be a bit odd because the > > > > application is asking for some protection but no guarantees are given > > > > and the application is not made aware via an error code that there is a > > > > problem. Asking the application to parse dmesg hoping to find the right > > > > error message is going to be fragile. > > > > > > Its a actually a good question. > > > What should we be doing if a mix of isolcpus and housekeeping (aka > > > non-isolcpus) is given in the mask. > > > > > > Right now as you pointed, there is no easy way for the application to know > > > which are the non-isolcpus to set its affinity. cpusets effective_cpus and > > > cpus_allowed both will contain isolcpus too. > > > > The easy option is to not use isolcpus :-) It is a horrifically bad > > interface. > > Agree, but thats something thats been exposed long time back. > Do we have an option to remove that? Hopefully nobody is using it. >
I occasionally see bugs asking questions about interference from the kernel when isolcpus are in use. The last one was related to a timer interrupt every HZ (not a mainline kernel) but still, it's some evidence that it has users :(
-- Mel Gorman SUSE Labs
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