From patchwork Mon Jan 22 08:45:08 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 10177769 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E971460224 for ; Mon, 22 Jan 2018 09:06:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D833E27C0B for ; Mon, 22 Jan 2018 09:06:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CC76927DCD; Mon, 22 Jan 2018 09:06:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 24C9227C0B for ; Mon, 22 Jan 2018 09:06:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751876AbeAVIwk (ORCPT ); Mon, 22 Jan 2018 03:52:40 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:33722 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753343AbeAVIwj (ORCPT ); Mon, 22 Jan 2018 03:52:39 -0500 Received: from localhost (LFbn-1-12258-90.w90-92.abo.wanadoo.fr [90.92.71.90]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 30B5AF00; Mon, 22 Jan 2018 08:52:38 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Josh Snyder , Tejun Heo , Balbir Singh , Brendan Gregg , Jens Axboe , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , linux-block@vger.kernel.org, Ingo Molnar Subject: [PATCH 4.14 28/89] delayacct: Account blkio completion on the correct task Date: Mon, 22 Jan 2018 09:45:08 +0100 Message-Id: <20180122083957.481864595@linuxfoundation.org> X-Mailer: git-send-email 2.16.0 In-Reply-To: <20180122083954.683903493@linuxfoundation.org> References: <20180122083954.683903493@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Snyder commit c96f5471ce7d2aefd0dda560cc23f08ab00bc65d upstream. Before commit: e33a9bba85a8 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler") delayacct_blkio_end() was called after context-switching into the task which completed I/O. This resulted in double counting: the task would account a delay both waiting for I/O and for time spent in the runqueue. With e33a9bba85a8, delayacct_blkio_end() is called by try_to_wake_up(). In ttwu, we have not yet context-switched. This is more correct, in that the delay accounting ends when the I/O is complete. But delayacct_blkio_end() relies on 'get_current()', and we have not yet context-switched into the task whose I/O completed. This results in the wrong task having its delay accounting statistics updated. Instead of doing that, pass the task_struct being woken to delayacct_blkio_end(), so that it can update the statistics of the correct task. Signed-off-by: Josh Snyder Acked-by: Tejun Heo Acked-by: Balbir Singh Cc: Brendan Gregg Cc: Jens Axboe Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-block@vger.kernel.org Fixes: e33a9bba85a8 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler") Link: http://lkml.kernel.org/r/1513613712-571-1-git-send-email-joshs@netflix.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- include/linux/delayacct.h | 8 ++++---- kernel/delayacct.c | 42 ++++++++++++++++++++++++++---------------- kernel/sched/core.c | 6 +++--- 3 files changed, 33 insertions(+), 23 deletions(-) --- a/include/linux/delayacct.h +++ b/include/linux/delayacct.h @@ -71,7 +71,7 @@ extern void delayacct_init(void); extern void __delayacct_tsk_init(struct task_struct *); extern void __delayacct_tsk_exit(struct task_struct *); extern void __delayacct_blkio_start(void); -extern void __delayacct_blkio_end(void); +extern void __delayacct_blkio_end(struct task_struct *); extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *); extern __u64 __delayacct_blkio_ticks(struct task_struct *); extern void __delayacct_freepages_start(void); @@ -122,10 +122,10 @@ static inline void delayacct_blkio_start __delayacct_blkio_start(); } -static inline void delayacct_blkio_end(void) +static inline void delayacct_blkio_end(struct task_struct *p) { if (current->delays) - __delayacct_blkio_end(); + __delayacct_blkio_end(p); delayacct_clear_flag(DELAYACCT_PF_BLKIO); } @@ -169,7 +169,7 @@ static inline void delayacct_tsk_free(st {} static inline void delayacct_blkio_start(void) {} -static inline void delayacct_blkio_end(void) +static inline void delayacct_blkio_end(struct task_struct *p) {} static inline int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk) --- a/kernel/delayacct.c +++ b/kernel/delayacct.c @@ -51,16 +51,16 @@ void __delayacct_tsk_init(struct task_st * Finish delay accounting for a statistic using its timestamps (@start), * accumalator (@total) and @count */ -static void delayacct_end(u64 *start, u64 *total, u32 *count) +static void delayacct_end(spinlock_t *lock, u64 *start, u64 *total, u32 *count) { s64 ns = ktime_get_ns() - *start; unsigned long flags; if (ns > 0) { - spin_lock_irqsave(¤t->delays->lock, flags); + spin_lock_irqsave(lock, flags); *total += ns; (*count)++; - spin_unlock_irqrestore(¤t->delays->lock, flags); + spin_unlock_irqrestore(lock, flags); } } @@ -69,17 +69,25 @@ void __delayacct_blkio_start(void) current->delays->blkio_start = ktime_get_ns(); } -void __delayacct_blkio_end(void) +/* + * We cannot rely on the `current` macro, as we haven't yet switched back to + * the process being woken. + */ +void __delayacct_blkio_end(struct task_struct *p) { - if (current->delays->flags & DELAYACCT_PF_SWAPIN) - /* Swapin block I/O */ - delayacct_end(¤t->delays->blkio_start, - ¤t->delays->swapin_delay, - ¤t->delays->swapin_count); - else /* Other block I/O */ - delayacct_end(¤t->delays->blkio_start, - ¤t->delays->blkio_delay, - ¤t->delays->blkio_count); + struct task_delay_info *delays = p->delays; + u64 *total; + u32 *count; + + if (p->delays->flags & DELAYACCT_PF_SWAPIN) { + total = &delays->swapin_delay; + count = &delays->swapin_count; + } else { + total = &delays->blkio_delay; + count = &delays->blkio_count; + } + + delayacct_end(&delays->lock, &delays->blkio_start, total, count); } int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk) @@ -153,8 +161,10 @@ void __delayacct_freepages_start(void) void __delayacct_freepages_end(void) { - delayacct_end(¤t->delays->freepages_start, - ¤t->delays->freepages_delay, - ¤t->delays->freepages_count); + delayacct_end( + ¤t->delays->lock, + ¤t->delays->freepages_start, + ¤t->delays->freepages_delay, + ¤t->delays->freepages_count); } --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2046,7 +2046,7 @@ try_to_wake_up(struct task_struct *p, un p->state = TASK_WAKING; if (p->in_iowait) { - delayacct_blkio_end(); + delayacct_blkio_end(p); atomic_dec(&task_rq(p)->nr_iowait); } @@ -2059,7 +2059,7 @@ try_to_wake_up(struct task_struct *p, un #else /* CONFIG_SMP */ if (p->in_iowait) { - delayacct_blkio_end(); + delayacct_blkio_end(p); atomic_dec(&task_rq(p)->nr_iowait); } @@ -2112,7 +2112,7 @@ static void try_to_wake_up_local(struct if (!task_on_rq_queued(p)) { if (p->in_iowait) { - delayacct_blkio_end(); + delayacct_blkio_end(p); atomic_dec(&rq->nr_iowait); } ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK);