From 347bd7f072ea8c36e4becf32c76ee7e96bc7b1c3 Mon Sep 17 00:00:00 2001 From: Thorsten Blum Date: Fri, 29 Mar 2024 17:02:30 +0100 Subject: [PATCH] tracing: Improve benchmark test performance by using do_div() 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); Link: https://lore.kernel.org/linux-trace-kernel/20240329160229.4874-2-thorsten.blum@toblux.com Signed-off-by: Thorsten Blum Signed-off-by: Steven Rostedt (Google) --- 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) {