linux-kernel - Re: [PATCH v1 2/3] perf record: apply affinity masks when reading mmap buffers

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Date:   Thu, 13 Dec 2018 09:26:47 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/3] perf record: apply affinity masks when reading
 mmap buffers

Hi,
On 12.12.2018 15:15, Jiri Olsa wrote:
> On Wed, Dec 12, 2018 at 10:40:22AM +0300, Alexey Budankov wrote:
> 
> SNIP
> 
>>  int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int cpu)
>>  {
>> +	int c, nr_cpus, node;
>>  	/*
>>  	 * The last one will be done at perf_mmap__consume(), so that we
>>  	 * make sure we don't prevent tools from consuming every last event in
>> @@ -344,6 +369,17 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int c
>>  	map->cpu = cpu;
>>  
>>  	CPU_ZERO(&map->affinity_mask);
>> +	if (mp->affinity == PERF_AFFINITY_NODE && cpu__max_node() > 1) {
>> +		nr_cpus = cpu_map__nr(mp->cpu_map);
>> +		node = cpu__get_node(map->cpu);
>> +		for (c = 0; c < nr_cpus; c++) {
>> +			if (cpu__get_node(c) == node) {
>> +				CPU_SET(c, &map->affinity_mask);
>> +			}
>> +		}
>> +	} else if (mp->affinity == PERF_AFFINITY_CPU) {
>> +		CPU_SET(map->cpu, &map->affinity_mask);
>> +	}
> 
> won't both of this end up in same mask?

For tested dual socket 44 core broadwell:

		node 0		node 1
cpu mask	0-21,44-65  	22-43,66-87

For affinity=node map->affinity_mask is either [0-21,44-65] or [22-43,66-87].
For affinity=cpu  map->affinity_mask is [0] or [1] or [2] and so on.

Without affinity option set map->affinity_mask and record->affinity_mask are [].

Thanks,
Alexey

> 
> jirka
>