From nobody Tue Dec 16 11:05:14 2025 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (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 D53251C0DC0 for ; Thu, 20 Jun 2024 17:33:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718904787; cv=none; b=N1Ehflowy0hQReHm+ZIWFmBqlJhGHzYdYMX5GC8GKTkEyELkaaO4T2Or8lzpCbcHISE8CoMIl++JIv4wP+e7bsbYUwbmAIrtJuxhLnbaxJnnD2q/i2VF8UpCiHUbQvbLYtCqRQtxUeMENPHPksIBFcLRCwxO4KLmqDrC4tEUk3k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718904787; c=relaxed/simple; bh=AaKb7xH3D6322u5oRmwnJltCEtxp6IvHn7eAt659z8I=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=shWU1uduqB87O0oohF+NCax75JjMc91Pf1ccGltk85K8/10Ar0oBZ6GBZR3oQJeEtu+cNMwwrI3dO4SFU3UMfndrFmVvXex7kIA6ufcElAxmrvngoOmh+tXPJku3xdRvrd2hBKZfrWwgfOJXYFAMDUqAbHgdEOzEksE/AJlFH24= 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=eSWHo8M4; arc=none smtp.client-ip=209.85.219.201 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="eSWHo8M4" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dff1eb1c1fcso2176466276.0 for ; Thu, 20 Jun 2024 10:33:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1718904785; x=1719509585; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=FxbUlqEIru4E7gX2WnN1T22F/48gDP0UMTSnaKBJ4Lc=; b=eSWHo8M4VOVFdy0hf7i25uBcyd5QD7kYB+vH8Ur6a8X9zrr5Kdy4NI9Bh4fePQhrr/ KlTYR8dUlD60cPl9pQzGfCTmNyCL8TsJZwRNsfq1qd+vl9WVWrCNAqkox0ex4eZT5XnF /ZhHMoEVaqLlWb2mDVAPwrfty4pZbi0aFXWqqpqNSzCYGJ75VL2kyXO8LsuTkwNcISDf +Mb6uWxqvUS7hrTqNQNRkwc4mc46Vqt01iIiQsCeiULYI8thGXMsiDs6DLWugL3M7aru LG+1aakbRd9nZTw/SVABZQBq47og2C3CJWV2rFNoYCpnJkPWQsEb757WO+Nr5PLzdeSL FTIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718904785; x=1719509585; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=FxbUlqEIru4E7gX2WnN1T22F/48gDP0UMTSnaKBJ4Lc=; b=SEGC3so5quk+Ag9AyctW/shXxm4WrtDyLH8woFwwDweFZcLWeA9FJUAQgpmgT6UOsV 7pL1HJdkEIOela6JZUMnBVh1fsUSiLfDQSgSX8c6XTos8Bm6gxVG4bJwpFBy8gQpBOC/ YB39z3qOshbW8IbGnRlwiQaoB6JXQymSoH5WZaXsV5r7lcufHCoFnDpIDObohCIFjBcp 6fMy28nZm+W4o/Nlsf5waCVKRhokkpfUCqq5FB6zj4Sp5c/+QctZAezqtHxfPPS4qgIr xeInQ4VKvoY8ihUXhDnMrlu5+XOF7zyTDLIgXtXSoJzNLs/86unszOtvTqa/H9SJcdAs v/tQ== X-Gm-Message-State: AOJu0YwSlqLNdsjfEbd7/rMllA88ud5ZL5x7pYoViZFHJUh1h6z93Odj 8nestN7MyF6PlzEFR5Qt7pXajzO7lAxPRv5WfQoAgPSzGicjBWsLnsE4En7LS2ncYs3h0p02CQb XxIgzplyzLcj2OLorT/UmFIG1MT1TeBybLBXIiEmkt6eBKKofVQ0idAvwT4/0Ho+TR0C8fMtHNP ECTLqAdD43Ly24NATHm8e0QrYDm8dyY0NOzpR/806h92t8 X-Google-Smtp-Source: AGHT+IHaP7Rj7bKnYJ7MWtjZwe4lSBiUsB0rCkavybCanBMTCd0BYHyPfenxphR36EJEjDUhH4U78MupPTyf X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a25:db10:0:b0:e02:c3c2:4b96 with SMTP id 3f1490d57ef6-e02c3c25615mr754700276.1.1718904784462; Thu, 20 Jun 2024 10:33:04 -0700 (PDT) Date: Thu, 20 Jun 2024 10:32:57 -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 2.45.2.741.gdbec12cfda-goog Message-ID: <20240620173301.1761679-1-jstultz@google.com> Subject: [PATCH v2] sched: Move psi_account_irqtime() out of update_rq_clock_task() hotpath From: John Stultz To: LKML Cc: John Stultz , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Johannes Weiner , Suren Baghdasaryan , Chengming Zhou , Thomas Gleixner , Frederic Weisbecker , Qais Yousef , Joel Fernandes , kernel-team@android.com, Chengming Zhou , Jimmy Shiu Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It was reported that in moving to 6.1, a larger then 10% regression was seen in the performance of clock_gettime(CLOCK_THREAD_CPUTIME_ID,...). Using a simple reproducer, I found: 5.10: 100000000 calls in 24345994193 ns =3D> 243.460 ns per call 100000000 calls in 24288172050 ns =3D> 242.882 ns per call 100000000 calls in 24289135225 ns =3D> 242.891 ns per call 6.1: 100000000 calls in 28248646742 ns =3D> 282.486 ns per call 100000000 calls in 28227055067 ns =3D> 282.271 ns per call 100000000 calls in 28177471287 ns =3D> 281.775 ns per call The cause of this was finally narrowed down to the addition of psi_account_irqtime() in update_rq_clock_task(), in commit 52b1364ba0b1 ("sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure"). In my initial attempt to resolve this, I leaned towards moving all accounting work out of the clock_gettime() call path, but it wasn't very pretty, so it will have to wait for a later deeper rework. Instead, Peter shared this approach: Rework psi_account_irqtime() to use its own psi_irq_time base for accounting, and move it out of the hotpath, calling it instead from sched_tick() and __schedule(). In testing this, we found the importance of ensuring psi_account_irqtime() is run under the rq_lock, which Johannes Weiner helpfully explained, so also add some lockdep annotations to make that requirement clear. With this change the performance is back in-line with 5.10: 6.1+fix: 100000000 calls in 24297324597 ns =3D> 242.973 ns per call 100000000 calls in 24318869234 ns =3D> 243.189 ns per call 100000000 calls in 24291564588 ns =3D> 242.916 ns per call 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: Daniel Bristot de Oliveira Cc: Valentin Schneider Cc: Johannes Weiner Cc: Suren Baghdasaryan Cc: Chengming Zhou Cc: Thomas Gleixner Cc: Frederic Weisbecker Cc: Qais Yousef Cc: Joel Fernandes Cc: kernel-team@android.com Reviewed-by: Chengming Zhou Reviewed-by: Qais Yousef Fixes: 52b1364ba0b1 ("sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure") Originally-by: Peter Zijlstra Reported-by: Jimmy Shiu Signed-off-by: John Stultz Acked-by: Johannes Weiner --- v2: * Added Fixed tag * Switched to (delta <=3D 0) comparision as suggested by Chengming Zhou * Added Reviewed-by tags --- kernel/sched/core.c | 7 +++++-- kernel/sched/psi.c | 21 ++++++++++++++++----- kernel/sched/sched.h | 1 + kernel/sched/stats.h | 11 ++++++++--- 4 files changed, 30 insertions(+), 10 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index bcf2c4cc0522..59ce0841eb1f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -723,7 +723,6 @@ static void update_rq_clock_task(struct rq *rq, s64 del= ta) =20 rq->prev_irq_time +=3D irq_delta; delta -=3D irq_delta; - psi_account_irqtime(rq->curr, irq_delta); delayacct_irq(rq->curr, irq_delta); #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING @@ -5665,7 +5664,7 @@ void sched_tick(void) { int cpu =3D smp_processor_id(); struct rq *rq =3D cpu_rq(cpu); - struct task_struct *curr =3D rq->curr; + struct task_struct *curr; struct rq_flags rf; unsigned long hw_pressure; u64 resched_latency; @@ -5677,6 +5676,9 @@ void sched_tick(void) =20 rq_lock(rq, &rf); =20 + curr =3D rq->curr; + psi_account_irqtime(rq, curr, NULL); + update_rq_clock(rq); hw_pressure =3D arch_scale_hw_pressure(cpu_of(rq)); update_hw_load_avg(rq_clock_task(rq), rq, hw_pressure); @@ -6737,6 +6739,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) ++*switch_count; =20 migrate_disable_switch(rq, prev); + psi_account_irqtime(rq, prev, next); psi_sched_switch(prev, next, !task_on_rq_queued(prev)); =20 trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state); diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 7b4aa5809c0f..c37ddcb642d5 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -773,6 +773,7 @@ static void psi_group_change(struct psi_group *group, i= nt cpu, enum psi_states s; u32 state_mask; =20 + lockdep_assert_rq_held(cpu_rq(cpu)); groupc =3D per_cpu_ptr(group->pcpu, cpu); =20 /* @@ -991,22 +992,32 @@ void psi_task_switch(struct task_struct *prev, struct= task_struct *next, } =20 #ifdef CONFIG_IRQ_TIME_ACCOUNTING -void psi_account_irqtime(struct task_struct *task, u32 delta) +void psi_account_irqtime(struct rq *rq, struct task_struct *curr, struct t= ask_struct *prev) { - int cpu =3D task_cpu(task); + int cpu =3D task_cpu(curr); struct psi_group *group; struct psi_group_cpu *groupc; - u64 now; + u64 now, irq; + s64 delta; =20 if (static_branch_likely(&psi_disabled)) return; =20 - if (!task->pid) + if (!curr->pid) + return; + + lockdep_assert_rq_held(rq); + group =3D task_psi_group(curr); + if (prev && task_psi_group(prev) =3D=3D group) return; =20 now =3D cpu_clock(cpu); + irq =3D irq_time_read(cpu); + delta =3D (s64)(irq - rq->psi_irq_time); + if (delta <=3D 0) + return; + rq->psi_irq_time =3D irq; =20 - group =3D task_psi_group(task); do { if (!group->enabled) continue; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index a831af102070..ef20c61004eb 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1126,6 +1126,7 @@ struct rq { =20 #ifdef CONFIG_IRQ_TIME_ACCOUNTING u64 prev_irq_time; + u64 psi_irq_time; #endif #ifdef CONFIG_PARAVIRT u64 prev_steal_time; diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h index 38f3698f5e5b..b02dfc322951 100644 --- a/kernel/sched/stats.h +++ b/kernel/sched/stats.h @@ -110,8 +110,12 @@ __schedstats_from_se(struct sched_entity *se) void psi_task_change(struct task_struct *task, int clear, int set); void psi_task_switch(struct task_struct *prev, struct task_struct *next, bool sleep); -void psi_account_irqtime(struct task_struct *task, u32 delta); - +#ifdef CONFIG_IRQ_TIME_ACCOUNTING +void psi_account_irqtime(struct rq *rq, struct task_struct *curr, struct t= ask_struct *prev); +#else +static inline void psi_account_irqtime(struct rq *rq, struct task_struct *= curr, + struct task_struct *prev) {} +#endif /*CONFIG_IRQ_TIME_ACCOUNTING */ /* * PSI tracks state that persists across sleeps, such as iowaits and * memory stalls. As a result, it has to distinguish between sleeps, @@ -192,7 +196,8 @@ static inline void psi_ttwu_dequeue(struct task_struct = *p) {} static inline void psi_sched_switch(struct task_struct *prev, struct task_struct *next, bool sleep) {} -static inline void psi_account_irqtime(struct task_struct *task, u32 delta= ) {} +static inline void psi_account_irqtime(struct rq *rq, struct task_struct *= curr, + struct task_struct *prev) {} #endif /* CONFIG_PSI */ =20 #ifdef CONFIG_SCHED_INFO --=20 2.45.2.741.gdbec12cfda-goog