From nobody Sat Feb 7 17:22:31 2026 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 554D8136988 for ; Tue, 22 Apr 2025 04:43:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745297040; cv=none; b=k1AJyIFfrqQKJsDSov9S8WykrkYvYD7lnxCY3mVqWDU9vDucgv1QODkeO4NkCnPlkuF2KVsj0gVr54AR5HiYPzDL8vmTNWEuEZxuzbSf1/oeRXKorl33Yh4jV5vzjeLEwsjpQfn8hNu63AG65pUxP41NVSlS/KaYHYfs5c2ycwI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745297040; c=relaxed/simple; bh=i+D2YEf/4fhpjjD1fZ+3R3wPVV39LN2fijYTdWl+sYc=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=dZAhjGbUDx2AFnlN0b3ESTYg60tIoiFLwB2E9AlrWqWRSoSpRWeI+KSoODYd+brKcxVF40ujalMbxF3BMmH6+VS7CY1EKNnGMpaTwzdzfWBx6U4FV3JtDXkLUUypJ9IyPCaKG8//+aoekZYftY+9t8yf5jnEQH4KOiPwNAKDz2E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=cnwVKfBm; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="cnwVKfBm" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-896c1845cb9so4275798a12.1 for ; Mon, 21 Apr 2025 21:43:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1745297038; x=1745901838; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=OMmFR27feHohiG2lQNR6bQsxIcQsMWncMxBCrcKvZNc=; b=cnwVKfBmIJp8TUFzrdq0hn3s74iwO4k0kNUg2UPiTvBK97CeTdmzGsjDI4Abi+upS3 ELCxEqBh+Xx2PZNolU46agi/ZJAWYUPIIe1Pr/H+HgUZjQQ4us8o3WIjYAVV7K85j7OT 1wB06+qEcSZvT6RuoTyHSjbZ8XZnbZnunCkbAYaj/dxiiuUv7jqSdu6GxOtf9+xdD/IP 9tEpNOOG2TMGWwZQl8OFD7hwT6A/FVkFjeB9CULBBnFSntZK9GxVb/UQn8J0whgSerW5 8tkVvDRa3IRWcmxim+sCibCrqOEV+wdok7EHAI6VKgSwv2XpvtF/bdkxThFiRSMVYgW7 PRWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1745297038; x=1745901838; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=OMmFR27feHohiG2lQNR6bQsxIcQsMWncMxBCrcKvZNc=; b=qSsDGR5p0hXctf/K6zw4Mgy5wZfNEpGSnBQ5W94jzVxu6JusyaXkUjc5DbYyeABMJF MvLtRLWPLGIq+zK5/Hm/UAdMO/GGsR29OnaXHNYNo8lnCR8daMK921J9gYenToiC7H2A qly6hMnelrrRnfg8YcWcLL9Ck4S/RuKFhUi3D76ENY4RhDIZUWz1BSoIC0p5ZSjCLO3i gTATGJd2xHEQptnzJNPE87QRRK2OwLunDCD0bjsGDtkkt/JWP/SQWY4+rprxgcwTvsRO AIMXvpdZ1pJHmvAdPRtVEeoNISlVQGMZdjSe7AqWdxmE+WnNJlabMKucfhg7J9PZNsnB IHCA== X-Gm-Message-State: AOJu0YyFW6A/7ucIGiG6H5tWMpXYVg9+69frgbVf0telvu1cxnJ5zG9E qk4spWxUhHMmFtuaf90xZlDgbR8BMW7E8JNARf2+nrdw8I0CPFAsQDIgDnZuop9BxRcfBc6Deel OpG94fZgujcZxTrkWK6yDzKop+0uKmMjUjQeh5YYsLhXx68llBFwNbcyhGcJAjhKc00F6zJJUKX QH2XyrHDG3xC1j+ntN4P82RY2freDwzPvbTcL/nr+37/Kt X-Google-Smtp-Source: AGHT+IF4a68nX6HkGf5QzDN5LJNE72LkorYborqQLUSbjAymqaQbDl+KAheVo/MycLLz2s798H+JIw0BOnBo X-Received: from pgbf37.prod.google.com ([2002:a63:5125:0:b0:af2:3b16:9767]) (user=jstultz job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:2d07:b0:1f3:323e:3743 with SMTP id adf61e73a8af0-203cc60d6bdmr19705780637.12.1745297038495; Mon, 21 Apr 2025 21:43:58 -0700 (PDT) Date: Mon, 21 Apr 2025 21:43:45 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.49.0.805.g082f7c87e0-goog Message-ID: <20250422044355.390780-1-jstultz@google.com> Subject: [RFC][PATCH] sched/core: Tweak wait_task_inactive() to force dequeue sched_delayed tasks From: John Stultz To: LKML Cc: John Stultz , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , kernel-team@android.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It was reported that in 6.12, smpboot_create_threads() was taking much longer then in 6.6. I narrowed down the call path to: smpboot_create_threads() -> kthread_create_on_cpu() -> kthread_bind() -> __kthread_bind_mask() ->wait_task_inactive() Where in wait_task_inactive() we were regularly hitting the queued case, which sets a 1 tick timeout, which when called multiple times in a row, accumulates quickly into a long delay. I noticed disabling the DELAY_DEQUEUE sched feature recovered the performance, and it seems the newly create tasks are usually sched_delayed and left on the runqueue. So in wait_task_inactive() when we see the task task_on_rq_queued(p) and p->se.sched_delayed, manually dequeue the sched_delayed task with DEQUEUE_DELAYED, so we don't have to constantly wait a tick. This seems to work, but I've only lightly tested it, so I'd love close review and feedback in case I've missed something in wait_task_inactive(), or if there is a simpler alternative approach. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Valentin Schneider Cc: K Prateek Nayak Cc: kernel-team@android.com Signed-off-by: John Stultz Tested-by: K Prateek Nayak --- kernel/sched/core.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c81cf642dba05..43f0931a3cd8a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2287,6 +2287,14 @@ unsigned long wait_task_inactive(struct task_struct = *p, unsigned int match_state running =3D task_on_cpu(rq, p); queued =3D task_on_rq_queued(p); ncsw =3D 0; + /* + * If task is sched_delayed, force dequeue it, to avoid always + * hitting the tick timeout in the queued case + */ + if (!running && queued && p->se.sched_delayed) { + dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED); + queued =3D task_on_rq_queued(p); + } if ((match =3D __task_state_match(p, match_state))) { /* * When matching on p->saved_state, consider this task --=20 2.49.0.805.g082f7c87e0-goog