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

[Jiri Olsa <jolsa@redhat.com>]

On Wed, Dec 12, 2018 at 10:40:22AM +0300, Alexey Budankov wrote:
> 
> Build node cpu masks for mmap data buffers. Bind AIO data buffers
> to nodes according to kernel data buffers location. Apply node cpu
> masks to trace reading thread every time it references memory cross
> node or cross cpu.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
>  tools/perf/builtin-record.c |  9 +++++++++
>  tools/perf/util/evlist.c    |  6 +++++-
>  tools/perf/util/mmap.c      | 38 ++++++++++++++++++++++++++++++++++++-
>  tools/perf/util/mmap.h      |  1 +
>  4 files changed, 52 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 4979719e54ae..1a1438c73f96 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -532,6 +532,9 @@ static int record__mmap_evlist(struct record *rec,
>  	struct record_opts *opts = &rec->opts;
>  	char msg[512];
>  
> +	if (opts->affinity != PERF_AFFINITY_SYS)
> +		cpu__setup_cpunode_map();
> +
>  	if (perf_evlist__mmap_ex(evlist, opts->mmap_pages,
>  				 opts->auxtrace_mmap_pages,
>  				 opts->auxtrace_snapshot_mode,
> @@ -751,6 +754,12 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
>  		struct perf_mmap *map = &maps[i];
>  
>  		if (map->base) {
> +			if (rec->opts.affinity != PERF_AFFINITY_SYS &&
> +			    !CPU_EQUAL(&rec->affinity_mask, &map->affinity_mask)) {
> +				CPU_ZERO(&rec->affinity_mask);
> +				CPU_OR(&rec->affinity_mask, &rec->affinity_mask, &map->affinity_mask);
> +				sched_setaffinity(0, sizeof(rec->affinity_mask), &rec->affinity_mask);
> +			}

hum, so you change affinity every time you read different map?
I'm surprised this is actualy faster..

anyway this patch is doing 2 things.. binding the memory allocation
to nodes and setting the process affinity, please seprate those and
explain the logic behind

thanks,
jirka