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Subject[Patch 5/7] synchronous block I/O delays
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Date
delayacct-blkio.patch

Record time spent by a task waiting for completion of
userspace initiated synchronous block I/O. This can help
determine the right I/O priority for the task.

Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>

fs/buffer.c | 3 +++
fs/read_write.c | 5 ++++-
include/linux/delayacct.h | 8 ++++++++
include/linux/sched.h | 2 ++
kernel/delayacct.c | 14 ++++++++++++++
mm/filemap.c | 5 ++++-
mm/memory.c | 8 +++++++-
7 files changed, 42 insertions(+), 3 deletions(-)
Index: linux-2.6.16-rc4/include/linux/delayacct.h
===================================================================
--- linux-2.6.16-rc4.orig/include/linux/delayacct.h 2006-02-27 01:52:56.000000000 -0500
+++ linux-2.6.16-rc4/include/linux/delayacct.h 2006-02-27 01:52:59.000000000 -0500
@@ -25,6 +25,7 @@ int delayacct_sysctl_handler(ctl_table *
extern int delayacct_init(void);
extern void __delayacct_tsk_init(struct task_struct *);
extern void __delayacct_tsk_exit(struct task_struct *);
+extern void __delayacct_blkio(void);

static inline void delayacct_tsk_early_init(struct task_struct *tsk)
{
@@ -48,6 +49,11 @@ static inline void delayacct_timestamp_s
if (unlikely(current->delays && delayacct_on))
do_posix_clock_monotonic_gettime(&current->delays->start);
}
+static inline void delayacct_blkio(void)
+{
+ if (unlikely(current->delays && delayacct_on))
+ __delayacct_blkio();
+}
#else
static inline void delayacct_tsk_early_init(struct task_struct *tsk)
{}
@@ -57,6 +63,8 @@ static inline void delayacct_tsk_exit(st
{}
static inline void delayacct_timestamp_start(void)
{}
+static inline void delayacct_blkio(void)
+{}
static inline int delayacct_init(void)
{}
#endif /* CONFIG_TASK_DELAY_ACCT */
Index: linux-2.6.16-rc4/kernel/delayacct.c
===================================================================
--- linux-2.6.16-rc4.orig/kernel/delayacct.c 2006-02-27 01:52:56.000000000 -0500
+++ linux-2.6.16-rc4/kernel/delayacct.c 2006-02-27 01:52:59.000000000 -0500
@@ -78,6 +78,20 @@ static inline nsec_t delayacct_measure(v
return timespec_diff_ns(&current->delays->start, &current->delays->end);
}

+void __delayacct_blkio(void)
+{
+ nsec_t delay;
+
+ delay = delayacct_measure();
+ if (delay < 0)
+ return;
+
+ spin_lock(&current->delays->lock);
+ current->delays->blkio_delay += delay;
+ current->delays->blkio_count++;
+ spin_unlock(&current->delays->lock);
+}
+
/* Allocate task_delay_info for all tasks without one */
static int alloc_delays(void)
{
Index: linux-2.6.16-rc4/fs/buffer.c
===================================================================
--- linux-2.6.16-rc4.orig/fs/buffer.c 2006-02-27 01:20:01.000000000 -0500
+++ linux-2.6.16-rc4/fs/buffer.c 2006-02-27 01:52:59.000000000 -0500
@@ -42,6 +42,7 @@
#include <linux/bitops.h>
#include <linux/mpage.h>
#include <linux/bit_spinlock.h>
+#include <linux/delayacct.h>

static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
static void invalidate_bh_lrus(void);
@@ -344,6 +345,7 @@ static long do_fsync(unsigned int fd, in
goto out_putf;
}

+ delayacct_timestamp_start();
mapping = file->f_mapping;

current->flags |= PF_SYNCWRITE;
@@ -366,6 +368,7 @@ static long do_fsync(unsigned int fd, in
out_putf:
fput(file);
out:
+ delayacct_blkio();
return ret;
}

Index: linux-2.6.16-rc4/fs/read_write.c
===================================================================
--- linux-2.6.16-rc4.orig/fs/read_write.c 2006-02-27 01:20:02.000000000 -0500
+++ linux-2.6.16-rc4/fs/read_write.c 2006-02-27 01:52:59.000000000 -0500
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
+#include <linux/delayacct.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -236,8 +237,10 @@ ssize_t do_sync_read(struct file *filp,
(ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos)))
wait_on_retry_sync_kiocb(&kiocb);

- if (-EIOCBQUEUED == ret)
+ if (-EIOCBQUEUED == ret) {
+ delayacct_timestamp_start();
ret = wait_on_sync_kiocb(&kiocb);
+ }
*ppos = kiocb.ki_pos;
return ret;
}
Index: linux-2.6.16-rc4/mm/filemap.c
===================================================================
--- linux-2.6.16-rc4.orig/mm/filemap.c 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/mm/filemap.c 2006-02-27 01:52:59.000000000 -0500
@@ -29,6 +29,7 @@
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/syscalls.h>
+#include <linux/delayacct.h>
#include "filemap.h"
/*
* FIXME: remove all knowledge of the buffer layer from the core VM
@@ -1084,8 +1085,10 @@ generic_file_read(struct file *filp, cha

init_sync_kiocb(&kiocb, filp);
ret = __generic_file_aio_read(&kiocb, &local_iov, 1, ppos);
- if (-EIOCBQUEUED == ret)
+ if (-EIOCBQUEUED == ret) {
+ delayacct_timestamp_start();
ret = wait_on_sync_kiocb(&kiocb);
+ }
return ret;
}

Index: linux-2.6.16-rc4/mm/memory.c
===================================================================
--- linux-2.6.16-rc4.orig/mm/memory.c 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/mm/memory.c 2006-02-27 01:52:59.000000000 -0500
@@ -48,6 +48,7 @@
#include <linux/rmap.h>
#include <linux/module.h>
#include <linux/init.h>
+#include <linux/delayacct.h>

#include <asm/pgalloc.h>
#include <asm/uaccess.h>
@@ -2208,12 +2209,17 @@ static inline int handle_pte_fault(struc

old_entry = entry = *pte;
if (!pte_present(entry)) {
+ delayacct_timestamp_start();
if (pte_none(entry)) {
+ int ret;
if (!vma->vm_ops || !vma->vm_ops->nopage)
return do_anonymous_page(mm, vma, address,
pte, pmd, write_access);
- return do_no_page(mm, vma, address,
+ ret = do_no_page(mm, vma, address,
pte, pmd, write_access);
+ if (vma->vm_file)
+ delayacct_blkio();
+ return ret;
}
if (pte_file(entry))
return do_file_page(mm, vma, address,
Index: linux-2.6.16-rc4/include/linux/sched.h
===================================================================
--- linux-2.6.16-rc4.orig/include/linux/sched.h 2006-02-27 01:52:54.000000000 -0500
+++ linux-2.6.16-rc4/include/linux/sched.h 2006-02-27 01:52:59.000000000 -0500
@@ -551,6 +551,8 @@ struct task_delay_info {
struct timespec start, end;

/* Add stats in pairs: u64 delay, u32 count, aligned properly */
+ u64 blkio_delay; /* wait for sync block io completion */
+ u32 blkio_count;
};
#endif


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