Commit 0ff92245 authored by Shailabh Nagar's avatar Shailabh Nagar Committed by Linus Torvalds

[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
......@@ -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
......@@ -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
......
......@@ -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);
}
......@@ -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;
}
......
......@@ -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);
......
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