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 1C83C1DDCE; Tue, 16 Jul 2024 16:04:40 +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=1721145880; cv=none; b=NGhf7Gfpt1EqmwNgFdfTDi8+u79gZYqKZU3cqjxkwcRC0nDhBPczLbsPhFG1cjb/H42kqkiQPrclXTxkXU9tDlxRNHqFdui7OjHsS29Fn1kNoCL2KhbYn4uHi3vPOla6wNWOFsjQkQQG4axKKLOC8dQ6Ef7dorC+wE11AMji5ZA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721145880; c=relaxed/simple; bh=Bk/aGZTsnpf9ncIiSmBHnd4x/Q7bbBRn/FZkfSr90ns=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kV6NspPGhDFghr7tTWgDfzweSXVlbU65JOJdyy+UZDgkdQcJ3nGOnkT9AZ13ixoy/RQZLeWGqQPbGu/txE4I6Ua975ZXD/ESIJuCiDKGrDaQvxQ5+E/pWmYrMRXT2MiTr0Ef6o82sZiErsY4iSBN2E7TbJioAg+6CR9PjeZPQAs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rwtI0T4k; 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="rwtI0T4k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D1CFC116B1; Tue, 16 Jul 2024 16:04:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1721145879; bh=Bk/aGZTsnpf9ncIiSmBHnd4x/Q7bbBRn/FZkfSr90ns=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rwtI0T4kAkeTmHuOm81aNd56cyQ36znAoufeypegedzXHmOK407YNfPvpYaQ3y4Ql AgLNazsj+Ifr6rDpj6FQ/w8UNZo2ZLUCboZLjxseUeELmr1uclRJ+fya1V5A/SXtBf 4DpxUVDGmcHihhKCO7UGnCgzCuRJm4Av2YaplOmc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jimmy Shiu , John Stultz , "Peter Zijlstra (Intel)" , Chengming Zhou , Qais Yousef Subject: [PATCH 6.6 108/121] sched: Move psi_account_irqtime() out of update_rq_clock_task() hotpath Date: Tue, 16 Jul 2024 17:32:50 +0200 Message-ID: <20240716152755.484904405@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240716152751.312512071@linuxfoundation.org> References: <20240716152751.312512071@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev 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: John Stultz commit ddae0ca2a8fe12d0e24ab10ba759c3fbd755ada8 upstream. 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 => 243.460 ns per call 100000000 calls in 24288172050 ns => 242.882 ns per call 100000000 calls in 24289135225 ns => 242.891 ns per call 6.1: 100000000 calls in 28248646742 ns => 282.486 ns per call 100000000 calls in 28227055067 ns => 282.271 ns per call 100000000 calls in 28177471287 ns => 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 => 242.973 ns per call 100000000 calls in 24318869234 ns => 243.189 ns per call 100000000 calls in 24291564588 ns => 242.916 ns per call Reported-by: Jimmy Shiu Originally-by: Peter Zijlstra Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Chengming Zhou Reviewed-by: Qais Yousef Link: https://lore.kernel.org/r/20240618215909.4099720-1-jstultz@google.com Fixes: 52b1364ba0b1 ("sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure") [jstultz: Fixed up minor collisions w/ 6.6-stable] Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- 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(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -722,7 +722,6 @@ static void update_rq_clock_task(struct rq->prev_irq_time += irq_delta; delta -= irq_delta; - psi_account_irqtime(rq->curr, irq_delta); delayacct_irq(rq->curr, irq_delta); #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING @@ -5641,7 +5640,7 @@ void scheduler_tick(void) { int cpu = smp_processor_id(); struct rq *rq = cpu_rq(cpu); - struct task_struct *curr = rq->curr; + struct task_struct *curr; struct rq_flags rf; unsigned long thermal_pressure; u64 resched_latency; @@ -5653,6 +5652,9 @@ void scheduler_tick(void) rq_lock(rq, &rf); + curr = rq->curr; + psi_account_irqtime(rq, curr, NULL); + update_rq_clock(rq); thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq)); update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure); @@ -6690,6 +6692,7 @@ static void __sched notrace __schedule(u ++*switch_count; migrate_disable_switch(rq, prev); + psi_account_irqtime(rq, prev, next); psi_sched_switch(prev, next, !task_on_rq_queued(prev)); trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state); --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -784,6 +784,7 @@ static void psi_group_change(struct psi_ enum psi_states s; u32 state_mask; + lockdep_assert_rq_held(cpu_rq(cpu)); groupc = per_cpu_ptr(group->pcpu, cpu); /* @@ -1002,19 +1003,29 @@ void psi_task_switch(struct task_struct } #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 task_struct *prev) { - int cpu = task_cpu(task); + int cpu = task_cpu(curr); struct psi_group *group; struct psi_group_cpu *groupc; - u64 now; + u64 now, irq; + s64 delta; - if (!task->pid) + if (!curr->pid) + return; + + lockdep_assert_rq_held(rq); + group = task_psi_group(curr); + if (prev && task_psi_group(prev) == group) return; now = cpu_clock(cpu); + irq = irq_time_read(cpu); + delta = (s64)(irq - rq->psi_irq_time); + if (delta < 0) + return; + rq->psi_irq_time = irq; - group = task_psi_group(task); do { if (!group->enabled) continue; --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1094,6 +1094,7 @@ struct rq { #ifdef CONFIG_IRQ_TIME_ACCOUNTING u64 prev_irq_time; + u64 psi_irq_time; #endif #ifdef CONFIG_PARAVIRT u64 prev_steal_time; --- a/kernel/sched/stats.h +++ b/kernel/sched/stats.h @@ -110,8 +110,12 @@ __schedstats_from_se(struct sched_entity 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 task_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(stru 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 */ #ifdef CONFIG_SCHED_INFO