Messages in this thread | | | Date | Wed, 23 Oct 2019 15:37:04 -0700 | From | Andi Kleen <> | Subject | Re: [PATCH v2 4/9] perf affinity: Add infrastructure to save/restore affinity |
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On Wed, Oct 23, 2019 at 09:08:47PM +0300, Alexey Budankov wrote: > On 23.10.2019 20:19, Andi Kleen wrote: > > On Wed, Oct 23, 2019 at 07:16:13PM +0300, Alexey Budankov wrote: > >> > >> On 23.10.2019 17:52, Andi Kleen wrote: > >>> On Wed, Oct 23, 2019 at 04:30:49PM +0200, Jiri Olsa wrote: > >>>> On Wed, Oct 23, 2019 at 06:02:35AM -0700, Andi Kleen wrote: > >>>>> On Wed, Oct 23, 2019 at 11:59:11AM +0200, Jiri Olsa wrote: > >>>>>> On Sun, Oct 20, 2019 at 10:51:57AM -0700, Andi Kleen wrote: > >>>>>> > >>>>>> SNIP > >>>>>> > >>>>>>> +} > >>>>>>> diff --git a/tools/perf/util/affinity.h b/tools/perf/util/affinity.h > >>>>>>> new file mode 100644 > >>>>>>> index 000000000000..e56148607e33 > >>>>>>> --- /dev/null > >>>>>>> +++ b/tools/perf/util/affinity.h > >>>>>>> @@ -0,0 +1,15 @@ > >>>>>>> +// SPDX-License-Identifier: GPL-2.0 > >>>>>>> +#ifndef AFFINITY_H > >>>>>>> +#define AFFINITY_H 1 > >>>>>>> + > >>>>>>> +struct affinity { > >>>>>>> + unsigned char *orig_cpus; > >>>>>>> + unsigned char *sched_cpus; > >>>>>> > >>>>>> why not use cpu_set_t directly? > >>>>> > >>>>> Because it's too small in glibc (only 1024 CPUs) and perf already > >>>>> supports more. > >>>> > >>>> nice, we're using it all over the place.. how about using bitmap_alloc? > >>> > >>> Okay. > >>> > >>> The other places is mainly perf record from Alexey's recent affinity changes. > >>> These probably need to be fixed. > >>> > >>> +Alexey > >> > >> Despite the issue indeed looks generic for stat and record modes, > >> have you already observed record startup overhead somewhere in your setups? > >> I would, first, prefer to reproduce the overhead, to have stable use case > >> for evaluation and then, possibly, improvement. > > > > What I meant the cpu_set usages you added in > > > > commit 9d2ed64587c045304efe8872b0258c30803d370c > > Author: Alexey Budankov <alexey.budankov@linux.intel.com> > > Date: Tue Jan 22 20:47:43 2019 +0300 > > > > perf record: Allocate affinity masks > > > > need to be fixed to allocate dynamically, or at least use MAX_NR_CPUs to > > support systems with >1024CPUs. That's an independent functionality > > problem. > > Oh, it is clear now. Thanks for pointing this out. For that to move from > cpu_mask_t to new custom struct affinity type its API requires extension > to provide mask operations similar to the ones that cpu_mask_t provides: > CPU_ZERO(), CPU_SET(), CPU_EQUAL(), CPU_OR(). > > For example it could be like: affinity__mask_zero(), affinity__mask_set(), > affinity__mask_equal(), affinity__mask_or() and then the collecting part > of record could also be moved to struct affinity type and overcome >1024CPUs > limitation.
Not sure you need to use my library, except perhaps the get_cpu_set_size() function. It is somewhat specialized.
Everything else you can use normal Linux bitmap functions, or call the sys call directly.
-Andi
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