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Subject[RFC][Patch 5/5] Per-task delay accounting: procfs interface
Creates /proc/<pid>/delay interface for getting per-task
delay statistics (time spent by a task waiting for cpu,
sync block I/O completion, swapping in pages etc.) The cpu
stats are available only if CONFIG_SCHEDSTATS is enabled.

The interface allows a task's delay stats (excluding cpu)
to be reset to zero. This is particularly useful if
delay accounting is being turned on/off dynamically.

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

fs/proc/base.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/delayacct.h | 6 ++++
kernel/delayacct.c | 33 +++++++++++++++++++++++
3 files changed, 104 insertions(+)
Index: linux-2.6.15-rc5/fs/proc/base.c
===================================================================
--- linux-2.6.15-rc5.orig/fs/proc/base.c
+++ linux-2.6.15-rc5/fs/proc/base.c
@@ -71,6 +71,8 @@
#include <linux/cpuset.h>
#include <linux/audit.h>
#include <linux/poll.h>
+#include <linux/delayacct.h>
+#include <linux/kernel.h>
#include "internal.h"

/*
@@ -166,6 +168,10 @@ enum pid_directory_inos {
PROC_TID_OOM_SCORE,
PROC_TID_OOM_ADJUST,

+#ifdef CONFIG_TASK_DELAY_ACCT
+ PROC_TID_DELAY_ACCT,
+ PROC_TGID_DELAY_ACCT,
+#endif
/* Add new entries before this */
PROC_TID_FD_DIR = 0x8000, /* 0x8000-0xffff */
};
@@ -220,6 +226,9 @@ static struct pid_entry tgid_base_stuff[
#ifdef CONFIG_AUDITSYSCALL
E(PROC_TGID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
#endif
+#ifdef CONFIG_TASK_DELAY_ACCT
+ E(PROC_TGID_DELAY_ACCT,"delay", S_IFREG|S_IRUGO),
+#endif
{0,0,NULL,0}
};
static struct pid_entry tid_base_stuff[] = {
@@ -262,6 +271,9 @@ static struct pid_entry tid_base_stuff[]
#ifdef CONFIG_AUDITSYSCALL
E(PROC_TID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
#endif
+#ifdef CONFIG_TASK_DELAY_ACCT
+ E(PROC_TID_DELAY_ACCT,"delay", S_IFREG|S_IRUGO),
+#endif
{0,0,NULL,0}
};

@@ -1066,6 +1078,53 @@ static struct file_operations proc_secco
};
#endif /* CONFIG_SECCOMP */

+#ifdef CONFIG_TASK_DELAY_ACCT
+ssize_t proc_delayacct_write(struct file *file, const char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct task_struct *tsk = proc_task(file->f_dentry->d_inode);
+ char kbuf[DELAYACCT_PROC_MAX_WRITE + 1];
+ int cmd, ret;
+
+ if (count > DELAYACCT_PROC_MAX_WRITE)
+ return -EINVAL;
+ if (copy_from_user(&kbuf, buffer, count))
+ return -EFAULT;
+
+ cmd = simple_strtoul(kbuf, NULL, 10);
+ ret = delayacct_task_write(tsk, cmd);
+
+ if (ret)
+ return ret;
+ return count;
+}
+
+ssize_t proc_delayacct_read(struct file *file, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct task_struct *tsk = proc_task(file->f_dentry->d_inode);
+ char kbuf[DELAYACCT_PROC_MAX_READ + 1];
+ size_t len;
+ loff_t __ppos = *ppos;
+
+ len = delayacct_task_read(tsk, kbuf);
+
+ if (__ppos >= len)
+ return 0;
+ if (count > len-__ppos)
+ count = len-__ppos;
+ if (copy_to_user(buffer, kbuf + __ppos, count))
+ return -EFAULT;
+ *ppos = __ppos + count;
+ return count;
+}
+
+static struct file_operations proc_delayacct_operations = {
+ .read = proc_delayacct_read,
+ .write = proc_delayacct_write,
+};
+#endif
+
static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
{
struct inode *inode = dentry->d_inode;
@@ -1786,6 +1845,12 @@ static struct dentry *proc_pident_lookup
inode->i_fop = &proc_loginuid_operations;
break;
#endif
+#ifdef CONFIG_TASK_DELAY_ACCT
+ case PROC_TID_DELAY_ACCT:
+ case PROC_TGID_DELAY_ACCT:
+ inode->i_fop = &proc_delayacct_operations;
+ break;
+#endif
default:
printk("procfs: impossible type (%d)",p->type);
iput(inode);
Index: linux-2.6.15-rc5/include/linux/delayacct.h
===================================================================
--- linux-2.6.15-rc5.orig/include/linux/delayacct.h
+++ linux-2.6.15-rc5/include/linux/delayacct.h
@@ -16,11 +16,17 @@

#include <linux/sched.h>

+/* Maximum data that a user can read/write from/to /proc/<tgid>/delay */
+#define DELAYACCT_PROC_MAX_READ 256
+#define DELAYACCT_PROC_MAX_WRITE 8
+
#ifdef CONFIG_TASK_DELAY_ACCT
extern int delayacct_on; /* Delay accounting turned on/off */
extern void delayacct_tsk_init(struct task_struct *tsk);
extern void delayacct_blkio(struct timespec *start, struct timespec *end);
extern void delayacct_swapin(struct timespec *start, struct timespec *end);
+extern int delayacct_task_write(struct task_struct *tsk, int cmd);
+extern size_t delayacct_task_read(struct task_struct *tsk, char *buf);
#else
static inline void delayacct_tsk_init(struct task_struct *tsk)
{}
Index: linux-2.6.15-rc5/kernel/delayacct.c
===================================================================
--- linux-2.6.15-rc5.orig/kernel/delayacct.c
+++ linux-2.6.15-rc5/kernel/delayacct.c
@@ -13,6 +13,7 @@

#include <linux/sched.h>
#include <linux/time.h>
+#include <linux/delayacct.h>

int delayacct_on; /* Delay accounting turned on/off */

@@ -65,3 +66,35 @@ inline void delayacct_swapin(struct time
current->delays.swapin_count++;
spin_unlock(&current->delays.lock);
}
+
+/* User writes @cmd to /proc/<tgid>/delay */
+inline int delayacct_task_write(struct task_struct *tsk, int cmd)
+{
+ if (cmd == 0) {
+ spin_lock(&tsk->delays.lock);
+ memset(&tsk->delays, 0, sizeof(tsk->delays));
+ spin_unlock(&tsk->delays.lock);
+ }
+ return 0;
+}
+
+/* User reads from /proc/<tgid>/delay */
+inline size_t delayacct_task_read(struct task_struct *tsk, char *buf)
+{
+ unsigned long long run_delay = 0;
+ unsigned long run_count = 0;
+
+#ifdef CONFIG_SCHEDSTATS
+ run_delay = jiffies_to_usecs(tsk->sched_info.run_delay) * 1000;
+ run_count = tsk->sched_info.pcnt ;
+#endif
+ return snprintf(buf, DELAYACCT_PROC_MAX_READ,
+ "%lu %llu %llu %u %llu %u %llu\n",
+ run_count,
+ (uint64_t) current_sched_time(tsk),
+ (uint64_t) run_delay,
+ (unsigned int) tsk->delays.blkio_count,
+ (uint64_t) tsk->delays.blkio_delay,
+ (unsigned int) tsk->delays.swapin_count,
+ (uint64_t) tsk->delays.swapin_delay);
+}
-
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