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Wed, 08 Jan 2025 23:53:07 -0800 (PST) X-Google-Smtp-Source: AGHT+IEEEiUGlJ10Kc8Mh22kcaQUJV1JNv8LIMdR5nsQVb0+EmtKA1fprNXE6lw3tD9o0QflpgqiqA== X-Received: by 2002:a05:620a:248d:b0:7a9:abdf:f517 with SMTP id af79cd13be357-7bce1286ea9mr359753885a.25.1736409186814; Wed, 08 Jan 2025 23:53:06 -0800 (PST) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.30]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7bce3248514sm42623685a.28.2025.01.08.23.53.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jan 2025 23:53:06 -0800 (PST) Message-ID: Subject: Re: [PATCH 1/2] perf ftrace: Check min/max latency only with bucket range From: Gabriele Monaco To: Namhyung Kim , Arnaldo Carvalho de Melo , Ian Rogers , Kan Liang Cc: Jiri Olsa , Adrian Hunter , Peter Zijlstra , Ingo Molnar , LKML , linux-perf-users@vger.kernel.org Date: Thu, 09 Jan 2025 08:53:02 +0100 In-Reply-To: <20250108210015.1188531-1-namhyung@kernel.org> References: <20250108210015.1188531-1-namhyung@kernel.org> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.2 (3.54.2-1.fc41) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-01-08 at 13:00 -0800, Namhyung Kim wrote: > It's an optional feature and remains 0 when bucket range is not > given. > And it makes the histogram goes to the last entry always because any > latency (num) is greater than or equal to 0. Thanks Namhyung for fixing this, something definitely slipped while testing.. I confirm your patches work well also when the bucket range is provided but= the min latency isn't. I'm wondering if it would be cleaner to propagate your changes (using min/max latency only if bucket_range is provided) also to make_histogram. That function currently works since we assume min_latency to be always 0, which is the case but probably not considering it altogether would look a bit better and prevent some headache in the future. --- tools/perf/builtin-ftrace.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c index 076c703e5c334..82d63d7af9d03 100644 --- a/tools/perf/builtin-ftrace.c +++ b/tools/perf/builtin-ftrace.c @@ -779,19 +779,16 @@ static void make_histogram(struct perf_ftrace *ftrace= , int buckets[], if (ftrace->use_nsec) num *=3D 1000; =20 - i =3D 0; - if (num < min_latency) - goto do_inc; - - num -=3D min_latency; - if (!ftrace->bucket_range) { i =3D log2(num); if (i < 0) i =3D 0; } else { - // Less than 1 unit (ms or ns), or, in the future, - // than the min latency desired. + i =3D 0; + if (num < min_latency) + goto do_inc; + + num -=3D min_latency; if (num > 0) // 1st entry: [ 1 unit .. bucket_range units ] i =3D num / ftrace->bucket_range + 1; if (num >=3D max_latency - min_latency) base-commit: 257ccfaf9fbef6f54eabf1a8f8a8efcc9036439b --=20 2.47.1