Linux kernel stable tree (mirror) https://git.radix-linux.su/kernel/linux.git/atom?h=linux-7.1.y 2025-05-13T19:36:22+00:00 2025-05-13T19:36:22+00:00 Ian Rogers irogers@google.com 2025-05-12T19:46:20+00:00 urn:sha1:375368a9617dbf843e563d9deb6bf45751f6d770 The existing fncache can get large in testing situations. As the bucket array is a fixed size this leads to it degrading to O(n) performance. Use a regular hashmap that can dynamically reallocate its array. Before: ``` $ time perf test "Parsing of PMU event table metrics" 10.3: Parsing of PMU event table metrics : Ok 10.4: Parsing of PMU event table metrics with fake PMUs : Ok real 0m14.132s user 0m17.806s sys 0m0.557s ``` After: ``` $ time perf test "Parsing of PMU event table metrics" 10.3: Parsing of PMU event table metrics : Ok 10.4: Parsing of PMU event table metrics with fake PMUs : Ok real 0m13.287s user 0m13.026s sys 0m0.532s ``` Committer notes: root@number:~# grep -m1 'model name' /proc/cpuinfo model name : AMD Ryzen 9 9950X3D 16-Core Processor root@number:~# Before: root@number:~# time perf test "Parsing of PMU event table metrics" 10.3: Parsing of PMU event table metrics : Ok 10.4: Parsing of PMU event table metrics with fake PMUs : Ok real 0m9.277s user 0m9.979s sys 0m0.055s root@number:~# After: root@number:~# time perf test "Parsing of PMU event table metrics" 10.3: Parsing of PMU event table metrics : Ok 10.4: Parsing of PMU event table metrics with fake PMUs : Ok real 0m9.296s user 0m9.361s sys 0m0.063s root@number:~# Signed-off-by: Ian Rogers <irogers@google.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Tested-by: Namhyung Kim <namhyung@kernel.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Clark <james.clark@linaro.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: Thomas Richter <tmricht@linux.ibm.com> Cc: Xu Yang <xu.yang_2@nxp.com> Link: https://lore.kernel.org/r/20250512194622.33258-2-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> 2019-11-28T11:08:38+00:00 Andi Kleen ak@linux.intel.com 2019-11-21T00:15:11+00:00 urn:sha1:d96645821e940bddff3fc5290656f83bf70d4c92 pmu.c does a lot of redundant /sys accesses while parsing aliases and probing for PMUs. On large systems with a lot of PMUs this can get expensive (>2s): % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 27.25 1.227847 8 160888 16976 openat 26.42 1.190481 7 164224 164077 stat Add a cache to remember if specific file names exist or don't exist, which eliminates most of this overhead. Also optimize some stat() calls to be slightly cheaper access() Resulting in: 0.18 0.004166 2 1851 305 open 0.08 0.001970 2 829 622 access Signed-off-by: Andi Kleen <ak@linux.intel.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: http://lore.kernel.org/lkml/20191121001522.180827-2-andi@firstfloor.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>