File perf-evsel-don-t-set-exclude_guest-by-default.patch of Package perf.29801
From: Ravi Bangoria <ravi.bangoria@amd.com>
Subject: perf evsel: Don't set exclude_guest by default
Date: Tue Nov 2 11:01:12 2021 +0530
Git-commit: eb39bf325631f9ae185abd16281079b7b9858737
References: jsc#SLE-24578 (dependent patch)
Signed-off-by: Tony Jones <tonyj@suse.de>
perf evsel: Don't set exclude_guest by default
Perf tool sets exclude_guest by default while calling perf_event_open().
Because IBS does not have filtering capability, it always gets rejected
by IBS PMU driver and thus perf falls back to non-precise sampling. Fix
it by not setting exclude_guest by default on AMD.
Before:
$ sudo ./perf record -C 0 -vvv true |& grep precise
precise_ip 3
decreasing precise_ip by one (2)
precise_ip 2
decreasing precise_ip by one (1)
precise_ip 1
decreasing precise_ip by one (0)
After:
$ sudo ./perf record -C 0 -vvv true |& grep precise
precise_ip 3
decreasing precise_ip by one (2)
precise_ip 2
Committer notes:
Fixup init to zero for perf_env in older compilers:
arch/x86/util/evsel.c:15:26: error: missing field 'os_release' initializer [-Werror,-Wmissing-field-initializers]
struct perf_env env = {0};
^
Committer notes:
Namhyung remarked:
It'd be nice if it can cover explicit "-e cycles:pp" as well.
Ravi clarified:
For explicit :pp modifier, evsel->precise_max does not get set and thus perf
does not try with different attr->precise_ip values while exclude_guest set.
So no issue with explicit :pp:
$ sudo ./perf record -C 0 -e cycles:pp -vvv |& grep "precise_ip\|exclude_guest"
precise_ip 2
exclude_guest 1
precise_ip 2
exclude_guest 1
switching off exclude_guest, exclude_host
precise_ip 2
^C
Also, with :P modifier, evsel->precise_max gets set but exclude_guest does
not and thus :P also works fine:
$ sudo ./perf record -C 0 -e cycles:P -vvv |& grep "precise_ip\|exclude_guest"
precise_ip 3
decreasing precise_ip by one (2)
precise_ip 2
^C
Reported-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20211103072112.32312-1-ravi.bangoria@amd.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/arch/x86/util/evsel.c b/tools/perf/arch/x86/util/evsel.c
index 2f733cdc8dbb..ac2899a25b7a 100644
--- a/tools/perf/arch/x86/util/evsel.c
+++ b/tools/perf/arch/x86/util/evsel.c
@@ -1,8 +1,31 @@
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
+#include <stdlib.h>
#include "util/evsel.h"
+#include "util/env.h"
+#include "linux/string.h"
void arch_evsel__set_sample_weight(struct evsel *evsel)
{
evsel__set_sample_bit(evsel, WEIGHT_STRUCT);
}
+
+void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr)
+{
+ struct perf_env env = { .total_mem = 0, } ;
+
+ if (!perf_env__cpuid(&env))
+ return;
+
+ /*
+ * On AMD, precise cycles event sampling internally uses IBS pmu.
+ * But IBS does not have filtering capabilities and perf by default
+ * sets exclude_guest = 1. This makes IBS pmu event init fail and
+ * thus perf ends up doing non-precise sampling. Avoid it by clearing
+ * exclude_guest.
+ */
+ if (env.cpuid && strstarts(env.cpuid, "AuthenticAMD"))
+ attr->exclude_guest = 0;
+
+ free(env.cpuid);
+}
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3cc1f8fcf15c..ec967fb8d7d9 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -294,7 +294,7 @@ static bool perf_event_can_profile_kernel(void)
return perf_event_paranoid_check(1);
}
-struct evsel *evsel__new_cycles(bool precise, __u32 type, __u64 config)
+struct evsel *evsel__new_cycles(bool precise __maybe_unused, __u32 type, __u64 config)
{
struct perf_event_attr attr = {
.type = type,
@@ -305,18 +305,16 @@ struct evsel *evsel__new_cycles(bool precise, __u32 type, __u64 config)
event_attr_init(&attr);
- if (!precise)
- goto new_event;
-
/*
* Now let the usual logic to set up the perf_event_attr defaults
* to kick in when we return and before perf_evsel__open() is called.
*/
-new_event:
evsel = evsel__new(&attr);
if (evsel == NULL)
goto out;
+ arch_evsel__fixup_new_cycles(&evsel->core.attr);
+
evsel->precise_max = true;
/* use asprintf() because free(evsel) assumes name is allocated */
@@ -1063,6 +1061,10 @@ void __weak arch_evsel__set_sample_weight(struct evsel *evsel)
evsel__set_sample_bit(evsel, WEIGHT);
}
+void __weak arch_evsel__fixup_new_cycles(struct perf_event_attr *attr __maybe_unused)
+{
+}
+
/*
* The enable_on_exec/disabled value strategy:
*
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index dcc87c2881b8..3ea687141afa 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -283,6 +283,7 @@ void __evsel__reset_sample_bit(struct evsel *evsel, enum perf_event_sample_forma
void evsel__set_sample_id(struct evsel *evsel, bool use_sample_identifier);
void arch_evsel__set_sample_weight(struct evsel *evsel);
+void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr);
int evsel__set_filter(struct evsel *evsel, const char *filter);
int evsel__append_tp_filter(struct evsel *evsel, const char *filter);
