Messages in this thread Patch in this message | | | From | Thorsten Blum <> | Subject | [PATCH v2] tracing: Improve performance by using do_div() | Date | Wed, 20 Mar 2024 22:55:41 +0100 |
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Partially revert commit d6cb38e10810 ("tracing: Use div64_u64() instead of do_div()") and use do_div() again to utilize its faster 64-by-32 division compared to the 64-by-64 division done by div64_u64().
Explicitly cast the divisor bm_cnt to u32 to prevent a Coccinelle warning reported by do_div.cocci. The warning was removed with commit d6cb38e10810 ("tracing: Use div64_u64() instead of do_div()").
Using the faster 64-by-32 division and casting bm_cnt to u32 is safe because we return early from trace_do_benchmark() if bm_cnt > UINT_MAX. This approach is already used twice in trace_do_benchmark() when calculating the standard deviation:
do_div(stddev, (u32)bm_cnt); do_div(stddev, (u32)bm_cnt - 1);
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com> --- Changes in v2: - Update patch with latest changes from master - Update patch title and description --- kernel/trace/trace_benchmark.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_benchmark.c b/kernel/trace/trace_benchmark.c index 811b08439406..e19c32f2a938 100644 --- a/kernel/trace/trace_benchmark.c +++ b/kernel/trace/trace_benchmark.c @@ -104,7 +104,7 @@ static void trace_do_benchmark(void) stddev = 0; delta = bm_total; - delta = div64_u64(delta, bm_cnt); + do_div(delta, (u32)bm_cnt); avg = delta; if (stddev > 0) { -- 2.44.0
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