From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792774041; b=0P/Udgk8NFDX/BkBKwNggwWYY/ezwaRp1MdR9JF4a2uCsBOyD19l7MfvLpk+OUUDatPk QoIL3QfZ5FkwhSUrrBKwSo2CRqcFu/0Wzb75MY6AVtpb/LLPI6GrWkXw+D3gZ6PVHLoTT S9duxsjnMqlzg7cLSGQNWixDdBBZy0Og/8fWntQB5O+fafAtRmecNcFwBMXbBArpoAhaQ pTDYMhy+aiCQ0UynED3GVZqGoh+1uiyue9HRmR7JNZMnTZ1wcXwUDo1vHipkSVqxaCb4N b+gzVsJnoT7YVUqThd6EPRHnFaEbyiw5jSKhtq3W+qe31RJyP7GzoQyhoFDkjRwMu6Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792774041; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=Tl+0007nuF1O7Sdc66qs0OU7IaKjZjhccfrTjc05XOc=; b=TR+oPYVnl/vUBAADO/I3iOClL1qrHMyAKIBkcz7o3A5TzHx90/rkcR103CWRUW3YpAN8 FAr6nwEqbZzW+qwe5HF9Ez8WIaRS1Qp4TtMjFB/vMxchYULl9PVWRKLZ8/kN+g9cQM01d h44hrqUiZn/yPw5VTdrwAXSR00ax4zxHjPCMBwSSIZA9ysQu9bU6dpUAjhgNxnquWo0vZ /65/CJs8YxU/FPxN6FgyC0raGqWrBrVvTMjlLtTz0lyhpaqAFrkN4cJfz22/dJSs+2cza H4gjZ+3YXQealnCesfWcLf7GtRD51apGDUztUJGD7pHYwZcnaidWNOi+b1XMaOFMolg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=tNzL1vbP; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40B75606A31A; Fri, 23 Oct 2026 16:47:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=tNzL1vbP Received: by smtp.kernel.org (Postfix) with ESMTPSA id 87F581F01825; Fri, 23 Oct 2026 16:47:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792774041; bh=Tl+0007nuF1O7Sdc66qs0OU7IaKjZjhccfrTjc05XOc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=tNzL1vbPVoZvmW5RvzYfL0LKzrc3zVelwi9+GlBnfIAWksNDBhJI2oQvbTrgpiYDy mPqGKqAefs3FMSGGLVgU6ljCxjKS44fnzfV441VkLe3ln0ZH+HRdF0vuIV8JZ2DM+0 c91tiRJ9Kt5eGrgbkshWBgfef2WlI+EwY9ShQxVw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Antoine Huret , "Peter Zijlstra (Intel)" Subject: [PATCH 6.18 094/193] perf: Update cgroup time when rotating multiplexed events Date: Fri, 23 Oct 2026 18:36:11 +0200 Message-ID: <20261023163716.428438807@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261023163714.201276352@linuxfoundation.org> References: <20261023163714.201276352@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Antoine Huret commit e4c7c401c6b9174c0c893084fdaa6a84bd2520d7 upstream. Since commit bd2756811766 ("perf: Rewrite core context handling"), perf_rotate_context() only updates the context time before scheduling out the flexible events. It no longer updates the cgroup time, which ctx_sched_out() used to do. Cgroup events take their times from the per-cpu cgroup clock, so between two cgroup switches the rotations see a frozen clock. The events rotated out lose the running time they accumulated, and the next update, usually a read, credits the whole interval to the events that happen to be on the PMU at that moment. As a result, the time_running of multiplexed cgroup events is wrong, and so are their scaled counts, as long as no other cgroup runs on the CPU, e.g. a busy job alone on its CPUs. Counting cycles over one second of a busy loop in a cgroup gives from half to several times the max frequency of the CPU. Update the cgroup time before rotating the CPU context, as was done before the rewrite. Fixes: bd2756811766 ("perf: Rewrite core context handling") Closes: https://lore.kernel.org/r/PR3PR07MB69223331EED5BEBE150375B7849C2@PR3PR07MB6922.eurprd07.prod.outlook.com/ Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Antoine Huret Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20261015-perf-cgroup-rotation-time-v1-1-93e177dfee5d@bull.com Signed-off-by: Greg Kroah-Hartman --- kernel/events/core.c | 1 + 1 file changed, 1 insertion(+) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4496,6 +4496,7 @@ static bool perf_rotate_context(struct p if (cpu_event) { update_context_time(&cpuctx->ctx); + update_cgrp_time_from_cpuctx(cpuctx, false); __pmu_ctx_sched_out(cpu_epc, EVENT_FLEXIBLE); rotate_ctx(&cpuctx->ctx, cpu_event); __pmu_ctx_sched_in(cpu_epc, EVENT_FLEXIBLE);