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Commit 0ff92245 authored by Shailabh Nagar's avatar Shailabh Nagar Committed by Linus Torvalds
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[PATCH] per-task-delay-accounting: sync block I/O and swapin delay collection 



Unlike earlier iterations of the delay accounting patches, now delays are only
collected for the actual I/O waits rather than try and cover the delays seen
in I/O submission paths.

Account separately for block I/O delays incurred as a result of swapin page
faults whose frequency can be affected by the task/process' rss limit.  Hence
swapin delays can act as feedback for rss limit changes independent of I/O
priority changes.

Signed-off-by: default avatarShailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: default avatarBalbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ca74e92b

include/linux/delayacct.h

+25 −0
Original line number Diff line number Diff line
@@ -19,6 +19,13 @@ 


#include <linux/sched.h>



/*

 * Per-task flags relevant to delay accounting

 * maintained privately to avoid exhausting similar flags in sched.h:PF_*

 * Used to set current->delays->flags

 */

#define DELAYACCT_PF_SWAPIN	0x00000001	/* I am doing a swapin */



#ifdef CONFIG_TASK_DELAY_ACCT



extern int delayacct_on;	/* Delay accounting turned on/off */
@@ -26,6 +33,8 @@ extern kmem_cache_t *delayacct_cache; 
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);



static inline void delayacct_set_flag(int flag)

{
@@ -53,6 +62,18 @@ static inline void delayacct_tsk_exit(struct task_struct *tsk) 
		__delayacct_tsk_exit(tsk);

}



static inline void delayacct_blkio_start(void)

{

	if (current->delays)

		__delayacct_blkio_start();

}



static inline void delayacct_blkio_end(void)

{

	if (current->delays)

		__delayacct_blkio_end();

}



#else

static inline void delayacct_set_flag(int flag)

{}
@@ -64,6 +85,10 @@ static inline void delayacct_tsk_init(struct task_struct *tsk) 
{}

static inline void delayacct_tsk_exit(struct task_struct *tsk)

{}

static inline void delayacct_blkio_start(void)

{}

static inline void delayacct_blkio_end(void)

{}

#endif /* CONFIG_TASK_DELAY_ACCT */



#endif

include/linux/sched.h

+13 −0
Original line number Diff line number Diff line
@@ -566,6 +566,19 @@ struct task_delay_info { 
	 * Atomicity of updates to XXX_delay, XXX_count protected by

	 * single lock above (split into XXX_lock if contention is an issue).

	 */



	/*

	 * XXX_count is incremented on every XXX operation, the delay

	 * associated with the operation is added to XXX_delay.

	 * XXX_delay contains the accumulated delay time in nanoseconds.

	 */

	struct timespec blkio_start, blkio_end;	/* Shared by blkio, swapin */

	u64 blkio_delay;	/* wait for sync block io completion */

	u64 swapin_delay;	/* wait for swapin block io completion */

	u32 blkio_count;	/* total count of the number of sync block */

				/* io operations performed */

	u32 swapin_count;	/* total count of the number of swapin block */

				/* io operations performed */

};

#endif

kernel/delayacct.c

+19 −0
Original line number Diff line number Diff line
@@ -85,3 +85,22 @@ static void delayacct_end(struct timespec *start, struct timespec *end, 
	spin_unlock(&current->delays->lock);

}



void __delayacct_blkio_start(void)

{

	delayacct_start(&current->delays->blkio_start);

}



void __delayacct_blkio_end(void)

{

	if (current->delays->flags & DELAYACCT_PF_SWAPIN)

		/* Swapin block I/O */

		delayacct_end(&current->delays->blkio_start,

			&current->delays->blkio_end,

			&current->delays->swapin_delay,

			&current->delays->swapin_count);

	else	/* Other block I/O */

		delayacct_end(&current->delays->blkio_start,

			&current->delays->blkio_end,

			&current->delays->blkio_delay,

			&current->delays->blkio_count);

}

kernel/sched.c

+5 −0
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ 
#include <linux/times.h>

#include <linux/acct.h>

#include <linux/kprobes.h>

#include <linux/delayacct.h>

#include <asm/tlb.h>



#include <asm/unistd.h>
@@ -4534,9 +4535,11 @@ void __sched io_schedule(void) 
{

	struct rq *rq = &__raw_get_cpu_var(runqueues);



	delayacct_blkio_start();

	atomic_inc(&rq->nr_iowait);

	schedule();

	atomic_dec(&rq->nr_iowait);

	delayacct_blkio_end();

}

EXPORT_SYMBOL(io_schedule);
@@ -4545,9 +4548,11 @@ long __sched io_schedule_timeout(long timeout) 
	struct rq *rq = &__raw_get_cpu_var(runqueues);

	long ret;



	delayacct_blkio_start();

	atomic_inc(&rq->nr_iowait);

	ret = schedule_timeout(timeout);

	atomic_dec(&rq->nr_iowait);

	delayacct_blkio_end();

	return ret;

}

mm/memory.c

+4 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ 
#include <linux/pagemap.h>

#include <linux/rmap.h>

#include <linux/module.h>

#include <linux/delayacct.h>

#include <linux/init.h>



#include <asm/pgalloc.h>
@@ -1934,6 +1935,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		migration_entry_wait(mm, pmd, address);

		goto out;

	}

	delayacct_set_flag(DELAYACCT_PF_SWAPIN);

	page = lookup_swap_cache(entry);

	if (!page) {

 		swapin_readahead(entry, address, vma);
@@ -1946,6 +1948,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, 
			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);

			if (likely(pte_same(*page_table, orig_pte)))

				ret = VM_FAULT_OOM;

			delayacct_clear_flag(DELAYACCT_PF_SWAPIN);

			goto unlock;

		}
@@ -1955,6 +1958,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		grab_swap_token();

	}



	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);

	mark_page_accessed(page);

	lock_page(page);