Messages in this thread Patch in this message | | | From | Kim Phillips <> | Subject | Re: [PATCH 2/2] perf tools: Improve IBS error handling | Date | Thu, 7 Oct 2021 14:17:27 -0500 |
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On 10/7/21 12:28 PM, Jiri Olsa wrote: > On Mon, Oct 04, 2021 at 04:41:14PM -0500, Kim Phillips wrote: >> --- >> tools/perf/util/evsel.c | 24 ++++++++++++++++++++++++ >> 1 file changed, 24 insertions(+) >> >> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >> index b915840690d4..f8a9cbd99314 100644 >> --- a/tools/perf/util/evsel.c >> +++ b/tools/perf/util/evsel.c >> @@ -2743,9 +2743,22 @@ static bool find_process(const char *name) >> return ret ? false : true; >> } >> >> +static bool is_amd(const char *arch, const char *cpuid) >> +{ >> + return arch && !strcmp("x86", arch) && cpuid && strstarts(cpuid, "AuthenticAMD"); >> +} >> + >> +static bool is_amd_ibs(struct evsel *evsel) >> +{ >> + return evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3); >> +} >> + >> int evsel__open_strerror(struct evsel *evsel, struct target *target, >> int err, char *msg, size_t size) >> { >> + struct perf_env *env = evsel__env(evsel); >> + const char *arch = perf_env__arch(env); >> + const char *cpuid = perf_env__cpuid(env); >> char sbuf[STRERR_BUFSIZE]; >> int printed = 0, enforced = 0; >> >> @@ -2841,6 +2854,17 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target, >> return scnprintf(msg, size, "wrong clockid (%d).", clockid); >> if (perf_missing_features.aux_output) >> return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel."); >> + if (is_amd(arch, cpuid)) { >> + if (is_amd_ibs(evsel)) { > > would single 'is_amd_ibs' call be better? checking on both amd and ibs
Good suggestion. If you look at the later patch in the BRS series, I have rewritten it to add the new AMD PMU like so:
if (is_amd()) { if (is_amd_ibs()) { if (evsel->this) return if (evsel->that) return } + if (is_amd_brs()) { + if (evsel->this) + return + if (evsel->that) + return + } }
Below is the full proposed replacement patch for patch 12 of 13 of the BRS series.
Another option is to have the is_amd_{ibs,brs} functions call is_amd() themselves, so the if (evsel->) code could be unindented by one tab, would that be better?
Thanks,
Kim
From a4cbab762719b30bddec2e278cf8b8eb82e83865 Mon Sep 17 00:00:00 2001 From: Stephane Eranian <eranian@google.com> Date: Thu, 9 Sep 2021 00:56:59 -0700 Subject: [PATCH] perf tools: Improve error handling of AMD Branch Sampling
This patch improves the error message printed by perf when perf_event_open() fails on AMD Zen3 when using the branch sampling feature. In the case of EINVAL, there are two main reasons: frequency mode or period is smaller than the depth of the branch sampling buffer (16). The patch checks the parameters of the call and tries to print a relevant message to explain the error:
$ perf record -b -e cpu/branch-brs/ -c 10 ls Error: AMD Branch Sampling does not support sampling period smaller than what is reported in /sys/devices/cpu/caps/branches.
$ perf record -b -e cpu/branch-brs/ ls Error: AMD Branch Sampling does not support frequency mode sampling, must pass a fixed sampling period via -c option or cpu/branch-brs,period=xxxx/.
Signed-off-by: Stephane Eranian <eranian@google.com> [Rebased on commit 9fe8895a27a84 ("perf env: Add perf_env__cpuid, perf_env__{nr_}pmu_mappings")] Signed-off-by: Kim Phillips <kim.phillips@amd.com> --- tools/perf/util/evsel.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index f8a9cbd99314..e1f5eff07355 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -2753,6 +2753,12 @@ static bool is_amd_ibs(struct evsel *evsel) return evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3); }
+static bool is_amd_brs(struct evsel *evsel) +{ + return ((evsel->core.attr.config & 0xff) == 0xc4) && + (evsel->core.attr.sample_type & PERF_SAMPLE_BRANCH_STACK); +} + int evsel__open_strerror(struct evsel *evsel, struct target *target, int err, char *msg, size_t size) { @@ -2863,6 +2869,14 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target, return scnprintf(msg, size, "AMD IBS may only be available in system-wide/per-cpu mode. Try using -a, or -C and workload affinity"); } + if (is_amd_brs(evsel)) { + if (evsel->core.attr.freq) + return scnprintf(msg, size, + "AMD Branch Sampling does not support frequency mode sampling, must pass a fixed sampling period via -c option or cpu/branch-brs,period=xxxx/."); + /* another reason is that the period is too small */ + return scnprintf(msg, size, + "AMD Branch Sampling does not support sampling period smaller than what is reported in /sys/devices/cpu/caps/branches."); + } }
break; -- 2.31.1
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