From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5F4DD22FF35; Mon, 2 Jun 2025 14:17:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748873876; cv=none; b=g6CAeM33mZ2km8BAglvB2/hDtpiqqnx7UQDmODmpsaiki5PVkkAT1jSOybBuXRmx6+BJmz5Jsy6bfNYVrKVG1Hwaa6J3PioUVP/wIiKq7NnzrTbrhu7H7lZBGPT/p3akdxadwXRkApam5XX7jtSlj+ktOD3R0gYtgm+NKISB77Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748873876; c=relaxed/simple; bh=5rIXr8KYko/w7oswBe8IEoVYTeou0KOSeG/v/9XBo68=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eX2tbcUeQgks76yA8h3olG9+k5dADI4sgVKANWzlOJx73s/I0ryJ0GoSSS/789G8G2N9BeDzfjB+qZpntHGMST5wIPvQAALj4ybJUzyPTZMqqQjjUxFc705ThI87iaNH/+IwBsfmAcXtZpx/ENDs9kEPizKugqt2D3ncfxj+v+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Gy7sptOx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Gy7sptOx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8F00C4CEEB; Mon, 2 Jun 2025 14:17:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1748873876; bh=5rIXr8KYko/w7oswBe8IEoVYTeou0KOSeG/v/9XBo68=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Gy7sptOx0oF9lbZSLm4ctCHNkU2OcS+TqfJg4LzuxBRLjRhOLYRixbbljnLD3XP+T 7llOh2bnlyTlzzs1RezvAm2GCjXmhzWpwvQ82RJsILJLo864PtEMNUjsF7ucMNQCqp CpGhkDdXBFKfXcrdn/JXNTCBQG/sd7MMVYIVEkRk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Peter Zijlstra (Intel)" , Kan Liang , Sasha Levin Subject: [PATCH 6.6 283/444] perf: Avoid the read if the count is already updated Date: Mon, 2 Jun 2025 15:45:47 +0200 Message-ID: <20250602134352.442663908@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250602134340.906731340@linuxfoundation.org> References: <20250602134340.906731340@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra (Intel) [ Upstream commit 8ce939a0fa194939cc1f92dbd8bc1a7806e7d40a ] The event may have been updated in the PMU-specific implementation, e.g., Intel PEBS counters snapshotting. The common code should not read and overwrite the value. The PERF_SAMPLE_READ in the data->sample_type can be used to detect whether the PMU-specific value is available. If yes, avoid the pmu->read() in the common code. Add a new flag, skip_read, to track the case. Factor out a perf_pmu_read() to clean up the code. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250121152303.3128733-3-kan.liang@linux.intel.com Signed-off-by: Sasha Levin --- include/linux/perf_event.h | 8 +++++++- kernel/events/core.c | 33 ++++++++++++++++----------------- kernel/events/ring_buffer.c | 1 + 3 files changed, 24 insertions(+), 18 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index fcb834dd75c24..90c782749b055 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1016,7 +1016,13 @@ struct perf_output_handle { struct perf_buffer *rb; unsigned long wakeup; unsigned long size; - u64 aux_flags; + union { + u64 flags; /* perf_output*() */ + u64 aux_flags; /* perf_aux_output*() */ + struct { + u64 skip_read : 1; + }; + }; union { void *addr; unsigned long head; diff --git a/kernel/events/core.c b/kernel/events/core.c index 987807b1040ae..5dd6424e62fa8 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1163,6 +1163,12 @@ static void perf_assert_pmu_disabled(struct pmu *pmu) WARN_ON_ONCE(*this_cpu_ptr(pmu->pmu_disable_count) == 0); } +static inline void perf_pmu_read(struct perf_event *event) +{ + if (event->state == PERF_EVENT_STATE_ACTIVE) + event->pmu->read(event); +} + static void get_ctx(struct perf_event_context *ctx) { refcount_inc(&ctx->refcount); @@ -3397,8 +3403,7 @@ static void __perf_event_sync_stat(struct perf_event *event, * we know the event must be on the current CPU, therefore we * don't need to use it. */ - if (event->state == PERF_EVENT_STATE_ACTIVE) - event->pmu->read(event); + perf_pmu_read(event); perf_event_update_time(event); @@ -4524,15 +4529,8 @@ static void __perf_event_read(void *info) pmu->read(event); - for_each_sibling_event(sub, event) { - if (sub->state == PERF_EVENT_STATE_ACTIVE) { - /* - * Use sibling's PMU rather than @event's since - * sibling could be on different (eg: software) PMU. - */ - sub->pmu->read(sub); - } - } + for_each_sibling_event(sub, event) + perf_pmu_read(sub); data->ret = pmu->commit_txn(pmu); @@ -7297,9 +7295,8 @@ static void perf_output_read_group(struct perf_output_handle *handle, if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) values[n++] = running; - if ((leader != event) && - (leader->state == PERF_EVENT_STATE_ACTIVE)) - leader->pmu->read(leader); + if ((leader != event) && !handle->skip_read) + perf_pmu_read(leader); values[n++] = perf_event_count(leader); if (read_format & PERF_FORMAT_ID) @@ -7312,9 +7309,8 @@ static void perf_output_read_group(struct perf_output_handle *handle, for_each_sibling_event(sub, leader) { n = 0; - if ((sub != event) && - (sub->state == PERF_EVENT_STATE_ACTIVE)) - sub->pmu->read(sub); + if ((sub != event) && !handle->skip_read) + perf_pmu_read(sub); values[n++] = perf_event_count(sub); if (read_format & PERF_FORMAT_ID) @@ -7369,6 +7365,9 @@ void perf_output_sample(struct perf_output_handle *handle, { u64 sample_type = data->type; + if (data->sample_flags & PERF_SAMPLE_READ) + handle->skip_read = 1; + perf_output_put(handle, *header); if (sample_type & PERF_SAMPLE_IDENTIFIER) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 52de76ef8723b..dc1193b779c08 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -181,6 +181,7 @@ __perf_output_begin(struct perf_output_handle *handle, handle->rb = rb; handle->event = event; + handle->flags = 0; have_lost = local_read(&rb->lost); if (unlikely(have_lost)) { -- 2.39.5