Re: [PATCH v2 4/9] perf affinity: Add infrastructure to save/restore affinity

Alexey Budankov
2019-10-23T16:16:20Z

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.

~Alexey