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Sun, 15 Nov 2026 07:15:07 -0800 (PST) Received: from thinkpad.lan ([2a06:c701:474b:1700:f61b:bfec:b5f1:a453]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49c5f1c0e31sm14556419f8f.19.2026.11.15.07.15.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Nov 2026 07:15:07 -0800 (PST) From: Avi Weiss To: peterz@infradead.org, namhyung@kernel.org Cc: mingo@redhat.com, acme@kernel.org, mark.rutland@arm.com, jolsa@kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] perf/core: Accumulate lost samples in inherited group reads Date: Sun, 15 Nov 2026 17:14:58 +0200 Message-ID: <20261115151458.258097-1-thnkslprpt@gmail.com> X-Mailer: git-send-email 2.53.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit `__perf_read_group_add()` accumulates event counts from inherited child events, but overwrites the `PERF_FORMAT_LOST` fields. A child reporting no losses therefore hides nonzero parent losses while it is alive. Accumulate `lost_samples` for the group leader and siblings so group reads preserve losses across inherited events. Fixes: 119a784c8127 ("perf/core: Add a new read format to get a number of lost samples") Signed-off-by: Avi Weiss --- kernel/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 457d75ea7142..165eb55608b6 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6163,14 +6163,14 @@ static int __perf_read_group_add(struct perf_event *leader, if (read_format & PERF_FORMAT_ID) values[n++] = primary_event_id(leader); if (read_format & PERF_FORMAT_LOST) - values[n++] = atomic64_read(&leader->lost_samples); + values[n++] += atomic64_read(&leader->lost_samples); for_each_sibling_event(sub, leader) { values[n++] += perf_event_count(sub, false); if (read_format & PERF_FORMAT_ID) values[n++] = primary_event_id(sub); if (read_format & PERF_FORMAT_LOST) - values[n++] = atomic64_read(&sub->lost_samples); + values[n++] += atomic64_read(&sub->lost_samples); } unlock: base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4 -- 2.53.0