linux-kernel - Re: [PATCH v2 3/3] perf record: adapt affinity to machines with #CPUs

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Date:   Mon, 25 Nov 2019 14:13:20 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] perf record: adapt affinity to machines with #CPUs
 > 1K

On 25.11.2019 12:42, Jiri Olsa wrote:
> On Mon, Nov 25, 2019 at 09:08:57AM +0300, Alexey Budankov wrote:
> 
> SNIP
> 
>> -static void perf_mmap__setup_affinity_mask(struct mmap *map, struct mmap_params *mp)
>> +static int perf_mmap__setup_affinity_mask(struct mmap *map, struct mmap_params *mp)
>>  {
>> -	CPU_ZERO(&map->affinity_mask);
>> +	map->affinity_mask.nbits = cpu__max_cpu();
>> +	map->affinity_mask.bits = bitmap_alloc(map->affinity_mask.nbits);
>> +	if (!map->affinity_mask.bits)
>> +		return -1;
>> +
>>  	if (mp->affinity == PERF_AFFINITY_NODE && cpu__max_node() > 1)
>>  		build_node_mask(cpu__get_node(map->core.cpu), &map->affinity_mask);
>>  	else if (mp->affinity == PERF_AFFINITY_CPU)
>> -		CPU_SET(map->core.cpu, &map->affinity_mask);
>> +		set_bit(map->core.cpu, map->affinity_mask.bits);
>> +
>> +	return 0;
>>  }
>>  
>> +#define MASK_SIZE 1023
>>  int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, int cpu)
>>  {
>> +	char mask[MASK_SIZE + 1] = {0};
> 
> does this need to be initialized?

This is to make sure the message is zero terminated for vfprintf call()

> 
>> +
>>  	if (perf_mmap__mmap(&map->core, &mp->core, fd, cpu)) {
>>  		pr_debug2("failed to mmap perf event ring buffer, error %d\n",
>>  			  errno);
>>  		return -1;
>>  	}
>>  
>> -	perf_mmap__setup_affinity_mask(map, mp);
>> +	if (perf_mmap__setup_affinity_mask(map, mp)) {
>> +		pr_debug2("failed to alloc mmap affinity mask, error %d\n",
>> +			  errno);
>> +		return -1;
>> +	}
>> +	bitmap_scnprintf(map->affinity_mask.bits, map->affinity_mask.nbits, mask, MASK_SIZE);
>> +	pr_debug2("%p: mmap mask[%ld]: %s\n", map, map->affinity_mask.nbits, mask);
> 
> the bitmap_scnprintf could be called only for debug case, right?

Right. It is required to prepare debug message.

> 
> 	if (version >= 2) {
> 		bitmap_scnprintf(map->affinity_mask.bits, map->affinity_mask.nbits, mask, MASK_SIZE);
> 		pr_debug2("%p: mmap mask[%ld]: %s\n", map, map->affinity_mask.nbits, mask);
> 	}
> 
> ditto int the record__adjust_affinity function
> 
> jirka
> 
> 

~Alexey