Re: [RFC PATCH v1 01/37] libperf cpumap: improve idx function
From: Arnaldo Carvalho de Melo <acme@kernel.org>
Date: 2021-08-31 18:46:40
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Em Sat, Aug 21, 2021 at 11:19:07AM +0200, Riccardo Mancini escreveu:
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From commit 7074674e7338863e ("perf cpumap: Maintain cpumaps orderedand without dups"), perf_cpu_map elements are sorted in ascending order. This patch improves the perf_cpu_map__idx function by using a binary search.
Why not use bsearch()? See 'man bsearch' and look at the example. - Arnaldo
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Signed-off-by: Riccardo Mancini <redacted> --- tools/lib/perf/cpumap.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c index ca0215047c326af4..fb633272be3aaed9 100644 --- a/tools/lib/perf/cpumap.c +++ b/tools/lib/perf/cpumap.c@@ -265,11 +265,18 @@ bool perf_cpu_map__empty(const struct perf_cpu_map *map) int perf_cpu_map__idx(struct perf_cpu_map *cpus, int cpu) { - int i; + int low = 0, high = cpus->nr, idx, cpu_at_idx; - for (i = 0; i < cpus->nr; ++i) { - if (cpus->map[i] == cpu) - return i; + while (low < high) { + idx = (low + high) / 2; + cpu_at_idx = cpus->map[idx]; + + if (cpu_at_idx == cpu) + return idx; + else if (cpu_at_idx > cpu) + high = idx; + else + low = idx+1; } return -1;-- 2.31.1
-- - Arnaldo