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c96f5471ce
Before commit:e33a9bba85("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. Withe33a9bba85, 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 <joshs@netflix.com> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Balbir Singh <bsingharora@gmail.com> Cc: <stable@vger.kernel.org> Cc: Brendan Gregg <bgregg@netflix.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-block@vger.kernel.org Fixes:e33a9bba85("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 <mingo@kernel.org>
189 lines
5.2 KiB
C
189 lines
5.2 KiB
C
/* delayacct.h - per-task delay accounting
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*
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* Copyright (C) Shailabh Nagar, IBM Corp. 2006
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU General Public License for more details.
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*
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*/
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#ifndef _LINUX_DELAYACCT_H
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#define _LINUX_DELAYACCT_H
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#include <uapi/linux/taskstats.h>
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/*
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* Per-task flags relevant to delay accounting
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* maintained privately to avoid exhausting similar flags in sched.h:PF_*
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* Used to set current->delays->flags
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*/
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#define DELAYACCT_PF_SWAPIN 0x00000001 /* I am doing a swapin */
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#define DELAYACCT_PF_BLKIO 0x00000002 /* I am waiting on IO */
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#ifdef CONFIG_TASK_DELAY_ACCT
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struct task_delay_info {
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spinlock_t lock;
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unsigned int flags; /* Private per-task flags */
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/* For each stat XXX, add following, aligned appropriately
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*
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* struct timespec XXX_start, XXX_end;
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* u64 XXX_delay;
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* u32 XXX_count;
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*
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* Atomicity of updates to XXX_delay, XXX_count protected by
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* single lock above (split into XXX_lock if contention is an issue).
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*/
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/*
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* XXX_count is incremented on every XXX operation, the delay
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* associated with the operation is added to XXX_delay.
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* XXX_delay contains the accumulated delay time in nanoseconds.
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*/
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u64 blkio_start; /* Shared by blkio, swapin */
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u64 blkio_delay; /* wait for sync block io completion */
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u64 swapin_delay; /* wait for swapin block io completion */
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u32 blkio_count; /* total count of the number of sync block */
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/* io operations performed */
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u32 swapin_count; /* total count of the number of swapin block */
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/* io operations performed */
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u64 freepages_start;
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u64 freepages_delay; /* wait for memory reclaim */
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u32 freepages_count; /* total count of memory reclaim */
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};
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#endif
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#include <linux/sched.h>
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#include <linux/slab.h>
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#ifdef CONFIG_TASK_DELAY_ACCT
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extern int delayacct_on; /* Delay accounting turned on/off */
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extern struct kmem_cache *delayacct_cache;
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extern void delayacct_init(void);
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extern void __delayacct_tsk_init(struct task_struct *);
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extern void __delayacct_tsk_exit(struct task_struct *);
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extern void __delayacct_blkio_start(void);
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extern void __delayacct_blkio_end(struct task_struct *);
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extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *);
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extern __u64 __delayacct_blkio_ticks(struct task_struct *);
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extern void __delayacct_freepages_start(void);
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extern void __delayacct_freepages_end(void);
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static inline int delayacct_is_task_waiting_on_io(struct task_struct *p)
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{
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if (p->delays)
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return (p->delays->flags & DELAYACCT_PF_BLKIO);
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else
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return 0;
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}
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static inline void delayacct_set_flag(int flag)
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{
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if (current->delays)
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current->delays->flags |= flag;
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}
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static inline void delayacct_clear_flag(int flag)
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{
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if (current->delays)
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current->delays->flags &= ~flag;
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}
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static inline void delayacct_tsk_init(struct task_struct *tsk)
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{
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/* reinitialize in case parent's non-null pointer was dup'ed*/
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tsk->delays = NULL;
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if (delayacct_on)
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__delayacct_tsk_init(tsk);
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}
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/* Free tsk->delays. Called from bad fork and __put_task_struct
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* where there's no risk of tsk->delays being accessed elsewhere
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*/
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static inline void delayacct_tsk_free(struct task_struct *tsk)
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{
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if (tsk->delays)
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kmem_cache_free(delayacct_cache, tsk->delays);
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tsk->delays = NULL;
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}
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static inline void delayacct_blkio_start(void)
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{
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delayacct_set_flag(DELAYACCT_PF_BLKIO);
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if (current->delays)
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__delayacct_blkio_start();
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}
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static inline void delayacct_blkio_end(struct task_struct *p)
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{
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if (current->delays)
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__delayacct_blkio_end(p);
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delayacct_clear_flag(DELAYACCT_PF_BLKIO);
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}
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static inline int delayacct_add_tsk(struct taskstats *d,
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struct task_struct *tsk)
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{
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if (!delayacct_on || !tsk->delays)
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return 0;
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return __delayacct_add_tsk(d, tsk);
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}
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static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
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{
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if (tsk->delays)
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return __delayacct_blkio_ticks(tsk);
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return 0;
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}
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static inline void delayacct_freepages_start(void)
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{
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if (current->delays)
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__delayacct_freepages_start();
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}
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static inline void delayacct_freepages_end(void)
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{
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if (current->delays)
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__delayacct_freepages_end();
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}
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#else
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static inline void delayacct_set_flag(int flag)
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{}
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static inline void delayacct_clear_flag(int flag)
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{}
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static inline void delayacct_init(void)
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{}
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static inline void delayacct_tsk_init(struct task_struct *tsk)
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{}
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static inline void delayacct_tsk_free(struct task_struct *tsk)
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{}
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static inline void delayacct_blkio_start(void)
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{}
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static inline void delayacct_blkio_end(struct task_struct *p)
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{}
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static inline int delayacct_add_tsk(struct taskstats *d,
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struct task_struct *tsk)
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{ return 0; }
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static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
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{ return 0; }
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static inline int delayacct_is_task_waiting_on_io(struct task_struct *p)
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{ return 0; }
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static inline void delayacct_freepages_start(void)
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{}
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static inline void delayacct_freepages_end(void)
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{}
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#endif /* CONFIG_TASK_DELAY_ACCT */
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#endif
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