lkml.org 
[lkml]   [2015]   [Oct]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3/5] perf, tools: Disable branch flags/cycles for --callgraph lbr
Date
From: Andi Kleen <ak@linux.intel.com>

Automatically disable collecting branch flags and cycles with
--call-graph lbr. This allows avoiding a bunch of extra MSR
reads in the PMI on Skylake.

When the kernel doesn't support the new flags they are automatically
cleared in the fallback code.

v2: Switch to use branch_sample_type instead of sample_type.
Adjust description.
Fix the fallback logic.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
tools/perf/util/evsel.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 8be867c..e8724b4 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -36,6 +36,7 @@ static struct {
bool cloexec;
bool clockid;
bool clockid_wrong;
+ bool lbr_flags;
} perf_missing_features;

static clockid_t clockid;
@@ -573,7 +574,9 @@ perf_evsel__config_callgraph(struct perf_evsel *evsel,
} else {
perf_evsel__set_sample_bit(evsel, BRANCH_STACK);
attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER |
- PERF_SAMPLE_BRANCH_CALL_STACK;
+ PERF_SAMPLE_BRANCH_CALL_STACK |
+ PERF_SAMPLE_BRANCH_NO_CYCLES |
+ PERF_SAMPLE_BRANCH_NO_FLAGS;
}
} else
pr_warning("Cannot use LBR callstack with branch stack. "
@@ -1312,6 +1315,9 @@ fallback_missing_features:
evsel->attr.mmap2 = 0;
if (perf_missing_features.exclude_guest)
evsel->attr.exclude_guest = evsel->attr.exclude_host = 0;
+ if (perf_missing_features.lbr_flags)
+ evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
+ PERF_SAMPLE_BRANCH_NO_CYCLES);
retry_sample_id:
if (perf_missing_features.sample_id_all)
evsel->attr.sample_id_all = 0;
@@ -1414,6 +1420,12 @@ try_fallback:
} else if (!perf_missing_features.sample_id_all) {
perf_missing_features.sample_id_all = true;
goto retry_sample_id;
+ } else if (!perf_missing_features.lbr_flags &&
+ (evsel->attr.branch_sample_type &
+ (PERF_SAMPLE_BRANCH_NO_CYCLES |
+ PERF_SAMPLE_BRANCH_NO_FLAGS))) {
+ perf_missing_features.lbr_flags = true;
+ goto fallback_missing_features;
}

out_close:
--
2.4.3


\
 
 \ /
  Last update: 2015-10-20 21:21    [W:0.104 / U:0.464 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site