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[82.135.80.212]) by smtp.gmail.com with ESMTPSA id an14-20020a17090656ce00b00a465b72a1f3sm5239507ejc.85.2024.03.20.15.02.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Mar 2024 15:02:18 -0700 (PDT) From: Thorsten Blum To: thorsten.blum@toblux.com Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, rostedt@goodmis.org Subject: [PATCH v2] tracing: Improve performance by using do_div() Date: Wed, 20 Mar 2024 22:55:41 +0100 Message-ID: <20240320215537.71034-5-thorsten.blum@toblux.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <4E5A47C3-E9DD-4FD2-BDC4-BED67EF791F2@toblux.com> References: <4E5A47C3-E9DD-4FD2-BDC4-BED67EF791F2@toblux.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- 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 =3D 0; =20 delta =3D bm_total; - delta =3D div64_u64(delta, bm_cnt); + do_div(delta, (u32)bm_cnt); avg =3D delta; =20 if (stddev > 0) { --=20 2.44.0