linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andi Kleen <andi@firstfloor.org>
To: acme@kernel.org
Cc: jolsa@kernel.org, linux-kernel@vger.kernel.org,
	Andi Kleen <ak@linux.intel.com>
Subject: [PATCH 02/12] perf affinity: Add infrastructure to save/restore affinity
Date: Wed, 20 Nov 2019 16:15:12 -0800	[thread overview]
Message-ID: <20191121001522.180827-3-andi@firstfloor.org> (raw)
In-Reply-To: <20191121001522.180827-1-andi@firstfloor.org>

From: Andi Kleen <ak@linux.intel.com>

The kernel perf subsystem has to IPI to the target CPU for many
operations. On systems with many CPUs and when managing many events the
overhead can be dominated by lots of IPIs.

An alternative is to set up CPU affinity in the perf tool, then set up
all the events for that CPU, and then move on to the next CPU.

Add some affinity management infrastructure to enable such a model.
Used in followon patches.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---

v2: Use linux/bitmap.h functions.
v3: Add affinity.c to the python-ext-sources to fix the python
interface.  Thanks 0day!
---
 tools/perf/util/Build              |  1 +
 tools/perf/util/affinity.c         | 72 ++++++++++++++++++++++++++++++
 tools/perf/util/affinity.h         | 15 +++++++
 tools/perf/util/python-ext-sources |  1 +
 4 files changed, 89 insertions(+)
 create mode 100644 tools/perf/util/affinity.c
 create mode 100644 tools/perf/util/affinity.h

diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index aab05e2c01a5..07da6c790b63 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -77,6 +77,7 @@ perf-y += sort.o
 perf-y += hist.o
 perf-y += util.o
 perf-y += cpumap.o
+perf-y += affinity.o
 perf-y += cputopo.o
 perf-y += cgroup.o
 perf-y += target.o
diff --git a/tools/perf/util/affinity.c b/tools/perf/util/affinity.c
new file mode 100644
index 000000000000..e197b0416f56
--- /dev/null
+++ b/tools/perf/util/affinity.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Manage affinity to optimize IPIs inside the kernel perf API. */
+#define _GNU_SOURCE 1
+#include <sched.h>
+#include <stdlib.h>
+#include <linux/bitmap.h>
+#include "perf.h"
+#include "cpumap.h"
+#include "affinity.h"
+
+static int get_cpu_set_size(void)
+{
+	int sz = cpu__max_cpu() + 8 - 1;
+	/*
+	 * sched_getaffinity doesn't like masks smaller than the kernel.
+	 * Hopefully that's big enough.
+	 */
+	if (sz < 4096)
+		sz = 4096;
+	return sz/8;
+}
+
+int affinity__setup(struct affinity *a)
+{
+	int cpu_set_size = get_cpu_set_size();
+
+	a->orig_cpus = bitmap_alloc(cpu_set_size*8);
+	if (!a->orig_cpus)
+		return -1;
+	sched_getaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
+	a->sched_cpus = bitmap_alloc(cpu_set_size*8);
+	if (!a->sched_cpus) {
+		free(a->orig_cpus);
+		return -1;
+	}
+	bitmap_zero((unsigned long *)a->sched_cpus, cpu_set_size);
+	a->changed = false;
+	return 0;
+}
+
+/*
+ * perf_event_open does an IPI internally to the target CPU.
+ * It is more efficient to change perf's affinity to the target
+ * CPU and then set up all events on that CPU, so we amortize
+ * CPU communication.
+ */
+void affinity__set(struct affinity *a, int cpu)
+{
+	int cpu_set_size = get_cpu_set_size();
+
+	if (cpu == -1)
+		return;
+	a->changed = true;
+	set_bit(cpu, a->sched_cpus);
+	/*
+	 * We ignore errors because affinity is just an optimization.
+	 * This could happen for example with isolated CPUs or cpusets.
+	 * In this case the IPIs inside the kernel's perf API still work.
+	 */
+	sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->sched_cpus);
+	clear_bit(cpu, a->sched_cpus);
+}
+
+void affinity__cleanup(struct affinity *a)
+{
+	int cpu_set_size = get_cpu_set_size();
+
+	if (a->changed)
+		sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
+	free(a->sched_cpus);
+	free(a->orig_cpus);
+}
diff --git a/tools/perf/util/affinity.h b/tools/perf/util/affinity.h
new file mode 100644
index 000000000000..008e2c3995b9
--- /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 long *orig_cpus;
+	unsigned long *sched_cpus;
+	bool changed;
+};
+
+void affinity__cleanup(struct affinity *a);
+void affinity__set(struct affinity *a, int cpu);
+int affinity__setup(struct affinity *a);
+
+#endif
diff --git a/tools/perf/util/python-ext-sources b/tools/perf/util/python-ext-sources
index 9af183860fbd..e7279ea6043a 100644
--- a/tools/perf/util/python-ext-sources
+++ b/tools/perf/util/python-ext-sources
@@ -33,3 +33,4 @@ util/trace-event.c
 util/string.c
 util/symbol_fprintf.c
 util/units.c
+util/affinity.c
-- 
2.23.0


  parent reply	other threads:[~2019-11-21  0:15 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-21  0:15 Optimize perf stat for large number of events/cpus Andi Kleen
2019-11-21  0:15 ` [PATCH 01/12] perf pmu: Use file system cache to optimize sysfs access Andi Kleen
2019-11-29  6:02   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` Andi Kleen [this message]
2019-11-29  6:02   ` [tip: perf/urgent] perf affinity: Add infrastructure to save/restore affinity tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 03/12] perf cpumap: Maintain cpumaps ordered and without dups Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 04/12] perf evlist: Maintain evlist->all_cpus Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 05/12] perf evsel: Add iterator to iterate over events ordered by CPU Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 06/12] perf evsel: Add functions to close evsel on a CPU Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 07/12] perf stat: Use affinity for closing file descriptors Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 08/12] perf stat: Factor out open error handling Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 09/12] perf stat: Use affinity for opening events Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-12-18  9:29   ` [perf stat] cc9cdf40ae: perf-sanity-tests.Event_times.fail kernel test robot
2019-11-21  0:15 ` [PATCH 10/12] perf stat: Use affinity for reading Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 11/12] perf evsel: Add functions to enable/disable for a specific CPU Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21  0:15 ` [PATCH 12/12] perf stat: Use affinity for enabling/disabling events Andi Kleen
2019-12-04  7:53   ` [tip: perf/urgent] " tip-bot2 for Andi Kleen
2019-11-21 12:47 ` Optimize perf stat for large number of events/cpus Andi Kleen
2019-11-21 14:32   ` Arnaldo Carvalho de Melo
2019-11-27 15:16 ` Arnaldo Carvalho de Melo
2019-11-27 15:43   ` Arnaldo Carvalho de Melo
2019-11-27 23:26     ` Andi Kleen
2019-11-28  0:01       ` Arnaldo Carvalho de Melo

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191121001522.180827-3-andi@firstfloor.org \
    --to=andi@firstfloor.org \
    --cc=acme@kernel.org \
    --cc=ak@linux.intel.com \
    --cc=jolsa@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [PATCH 02/12] perf affinity: Add infrastructure to save/restore affinity' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox