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Date:   Mon, 25 Nov 2019 12:21:22 +0100
From:   Jiri Olsa <jolsa@redhat.com>
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 3/3] perf record: adapt affinity to machines with
 #CPUs > 1K
Message-ID: <20191125112122.GA1201@krava>
References: <fb356fe9-ac87-71ab-9845-075b3fac3199@linux.intel.com>
 <69bd0062-0f9e-889b-b7ef-0d97d257569b@linux.intel.com>
 <20191125094220.GC4675@krava>
 <9b9209ce-ba61-824f-9443-3909991ff222@linux.intel.com>
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On Mon, Nov 25, 2019 at 02:13:20PM +0300, Alexey Budankov wrote:
> On 25.11.2019 12:42, Jiri Olsa wrote:
> > On Mon, Nov 25, 2019 at 09:08:57AM +0300, Alexey Budankov wrote:
> >=20
> > SNIP
> >=20
> >> -static void perf_mmap__setup_affinity_mask(struct mmap *map, struct m=
map_params *mp)
> >> +static int perf_mmap__setup_affinity_mask(struct mmap *map, struct mm=
ap_params *mp)
> >>  {
> >> -=09CPU_ZERO(&map->affinity_mask);
> >> +=09map->affinity_mask.nbits =3D cpu__max_cpu();
> >> +=09map->affinity_mask.bits =3D bitmap_alloc(map->affinity_mask.nbits)=
;
> >> +=09if (!map->affinity_mask.bits)
> >> +=09=09return -1;
> >> +
> >>  =09if (mp->affinity =3D=3D PERF_AFFINITY_NODE && cpu__max_node() > 1)
> >>  =09=09build_node_mask(cpu__get_node(map->core.cpu), &map->affinity_ma=
sk);
> >>  =09else if (mp->affinity =3D=3D PERF_AFFINITY_CPU)
> >> -=09=09CPU_SET(map->core.cpu, &map->affinity_mask);
> >> +=09=09set_bit(map->core.cpu, map->affinity_mask.bits);
> >> +
> >> +=09return 0;
> >>  }
> >> =20
> >> +#define MASK_SIZE 1023
> >>  int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, int =
cpu)
> >>  {
> >> +=09char mask[MASK_SIZE + 1] =3D {0};
> >=20
> > does this need to be initialized?
>=20
> This is to make sure the message is zero terminated for vfprintf call()

hum AFAICS it's used only in bitmap_scnprintf, which should
terminate the string properly

jirka

>=20
> >=20
> >> +
> >>  =09if (perf_mmap__mmap(&map->core, &mp->core, fd, cpu)) {
> >>  =09=09pr_debug2("failed to mmap perf event ring buffer, error %d\n",
> >>  =09=09=09  errno);
> >>  =09=09return -1;
> >>  =09}
> >> =20
> >> -=09perf_mmap__setup_affinity_mask(map, mp);
> >> +=09if (perf_mmap__setup_affinity_mask(map, mp)) {
> >> +=09=09pr_debug2("failed to alloc mmap affinity mask, error %d\n",
> >> +=09=09=09  errno);
> >> +=09=09return -1;
> >> +=09}
> >> +=09bitmap_scnprintf(map->affinity_mask.bits, map->affinity_mask.nbits=
, mask, MASK_SIZE);
> >> +=09pr_debug2("%p: mmap mask[%ld]: %s\n", map, map->affinity_mask.nbit=
s, mask);
> >=20
> > the bitmap_scnprintf could be called only for debug case, right?
>=20
> Right. It is required to prepare debug message.
>=20
> >=20
> > =09if (version >=3D 2) {
> > =09=09bitmap_scnprintf(map->affinity_mask.bits, map->affinity_mask.nbit=
s, mask, MASK_SIZE);
> > =09=09pr_debug2("%p: mmap mask[%ld]: %s\n", map, map->affinity_mask.nbi=
ts, mask);
> > =09}
> >=20
> > ditto int the record__adjust_affinity function
> >=20
> > jirka
> >=20
> >=20
>=20
> ~Alexey
>=20