[PATCH 1/1] task IO accounting: improve code readability

From: Andrea Righi
Date: Sun Jul 27 2008 - 11:29:31 EST

Put all i/o statistics in struct proc_io_accounting and use inline functions to
initialize and increment statistics, removing a lot of single variable
assignments.

This also reduces the kernel size as following (with CONFIG_TASK_XACCT=y and
CONFIG_TASK_IO_ACCOUNTING=y).

text data bss dec hex filename
11651 0 0 11651 2d83 kernel/exit.o.before
11619 0 0 11619 2d63 kernel/exit.o.after
10886 132 136 11154 2b92 kernel/fork.o.before
10758 132 136 11026 2b12 kernel/fork.o.after

3082029 807968 4818600 8708597 84e1f5 vmlinux.o.before
3081869 807968 4818600 8708437 84e155 vmlinux.o.after

Signed-off-by: Andrea Righi <righi.andrea@xxxxxxxxx>
---
fs/proc/base.c | 57 +++++++++-----------------------
include/linux/sched.h | 19 +++-------
include/linux/task_io_accounting.h | 27 +++++++++++++--
include/linux/task_io_accounting_ops.h | 56 +++++++++++++++++++++++++-----
kernel/exit.c | 30 ++---------------
kernel/fork.c | 15 +-------
kernel/tsacct.c | 14 ++++----
7 files changed, 104 insertions(+), 114 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index e74308b..3d94906 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -53,6 +53,7 @@
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
+#include <linux/task_io_accounting_ops.h>
#include <linux/init.h>
#include <linux/capability.h>
#include <linux/file.h>
@@ -2402,44 +2403,17 @@ static int proc_base_fill_cache(struct file *filp, void *dirent,
#ifdef CONFIG_TASK_IO_ACCOUNTING
static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
{
- u64 rchar, wchar, syscr, syscw;
- struct task_io_accounting ioac;
-
- rchar = task->rchar;
- wchar = task->wchar;
- syscr = task->syscr;
- syscw = task->syscw;
- memcpy(&ioac, &task->ioac, sizeof(ioac));
-
- if (whole) {
- unsigned long flags;
-
- if (lock_task_sighand(task, &flags)) {
- struct signal_struct *sig = task->signal;
- struct task_struct *t = task;
-
- rchar += sig->rchar;
- wchar += sig->wchar;
- syscr += sig->syscr;
- syscw += sig->syscw;
-
- ioac.read_bytes += sig->ioac.read_bytes;
- ioac.write_bytes += sig->ioac.write_bytes;
- ioac.cancelled_write_bytes +=
- sig->ioac.cancelled_write_bytes;
- while_each_thread(task, t) {
- rchar += t->rchar;
- wchar += t->wchar;
- syscr += t->syscr;
- syscw += t->syscw;
-
- ioac.read_bytes += t->ioac.read_bytes;
- ioac.write_bytes += t->ioac.write_bytes;
- ioac.cancelled_write_bytes +=
- t->ioac.cancelled_write_bytes;
- }
- unlock_task_sighand(task, &flags);
- }
+ struct proc_io_accounting acct = task->ioac;
+ unsigned long flags;
+
+ if (whole && lock_task_sighand(task, &flags)) {
+ struct task_struct *t = task;
+
+ task_io_accounting_add(&acct, &task->signal->ioac);
+ while_each_thread(task, t)
+ task_io_accounting_add(&acct, &t->ioac);
+
+ unlock_task_sighand(task, &flags);
}
return sprintf(buffer,
"rchar: %llu\n"
@@ -2449,9 +2423,10 @@ static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
"read_bytes: %llu\n"
"write_bytes: %llu\n"
"cancelled_write_bytes: %llu\n",
- rchar, wchar, syscr, syscw,
- ioac.read_bytes, ioac.write_bytes,
- ioac.cancelled_write_bytes);
+ acct.chr.rchar, acct.chr.wchar,
+ acct.chr.syscr, acct.chr.syscw,
+ acct.blk.read_bytes, acct.blk.write_bytes,
+ acct.blk.cancelled_write_bytes);
}

static int proc_tid_io_accounting(struct task_struct *task, char *buffer)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f59318a..034c1ca 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -505,10 +505,7 @@ struct signal_struct {
unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
unsigned long inblock, oublock, cinblock, coublock;
-#ifdef CONFIG_TASK_XACCT
- u64 rchar, wchar, syscr, syscw;
-#endif
- struct task_io_accounting ioac;
+ struct proc_io_accounting ioac;

/*
* Cumulative ns of scheduled CPU time for dead threads in the
@@ -1256,11 +1253,7 @@ struct task_struct {

unsigned long ptrace_message;
siginfo_t *last_siginfo; /* For ptrace use. */
-#ifdef CONFIG_TASK_XACCT
-/* i/o counters(bytes read/written, #syscalls */
- u64 rchar, wchar, syscr, syscw;
-#endif
- struct task_io_accounting ioac;
+ struct proc_io_accounting ioac;
#if defined(CONFIG_TASK_XACCT)
u64 acct_rss_mem1; /* accumulated rss usage */
u64 acct_vm_mem1; /* accumulated virtual memory usage */
@@ -2190,22 +2183,22 @@ extern long sched_group_rt_period(struct task_group *tg);
#ifdef CONFIG_TASK_XACCT
static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
{
- tsk->rchar += amt;
+ tsk->ioac.chr.rchar += amt;
}

static inline void add_wchar(struct task_struct *tsk, ssize_t amt)
{
- tsk->wchar += amt;
+ tsk->ioac.chr.wchar += amt;
}

static inline void inc_syscr(struct task_struct *tsk)
{
- tsk->syscr++;
+ tsk->ioac.chr.syscr++;
}

static inline void inc_syscw(struct task_struct *tsk)
{
- tsk->syscw++;
+ tsk->ioac.chr.syscw++;
}
#else
static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
diff --git a/include/linux/task_io_accounting.h b/include/linux/task_io_accounting.h
index 44d00e9..165390f 100644
--- a/include/linux/task_io_accounting.h
+++ b/include/linux/task_io_accounting.h
@@ -1,5 +1,5 @@
/*
- * task_io_accounting: a structure which is used for recording a single task's
+ * proc_io_accounting: a structure which is used for recording a single task's
* IO statistics.
*
* Don't include this header file directly - it is designed to be dragged in via
@@ -8,6 +8,22 @@
* Blame akpm@xxxxxxxx for all this.
*/

+#ifdef CONFIG_TASK_XACCT
+struct task_chr_io_accounting {
+ /* bytes read */
+ u64 rchar;
+ /* bytes written */
+ u64 wchar;
+ /* # of read syscalls */
+ u64 syscr;
+ /* # of write syscalls */
+ u64 syscw;
+};
+#else /* CONFIG_TASK_XACCT */
+struct task_chr_io_accounting {
+};
+#endif /* CONFIG_TASK_XACCT */
+
#ifdef CONFIG_TASK_IO_ACCOUNTING
struct task_io_accounting {
/*
@@ -31,7 +47,12 @@ struct task_io_accounting {
*/
u64 cancelled_write_bytes;
};
-#else
+#else /* CONFIG_TASK_IO_ACCOUNTING */
struct task_io_accounting {
};
-#endif
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+struct proc_io_accounting {
+ struct task_chr_io_accounting chr;
+ struct task_io_accounting blk;
+};
diff --git a/include/linux/task_io_accounting_ops.h b/include/linux/task_io_accounting_ops.h
index ff46c6f..e6f958e 100644
--- a/include/linux/task_io_accounting_ops.h
+++ b/include/linux/task_io_accounting_ops.h
@@ -9,7 +9,7 @@
#ifdef CONFIG_TASK_IO_ACCOUNTING
static inline void task_io_account_read(size_t bytes)
{
- current->ioac.read_bytes += bytes;
+ current->ioac.blk.read_bytes += bytes;
}

/*
@@ -18,12 +18,12 @@ static inline void task_io_account_read(size_t bytes)
*/
static inline unsigned long task_io_get_inblock(const struct task_struct *p)
{
- return p->ioac.read_bytes >> 9;
+ return p->ioac.blk.read_bytes >> 9;
}

static inline void task_io_account_write(size_t bytes)
{
- current->ioac.write_bytes += bytes;
+ current->ioac.blk.write_bytes += bytes;
}

/*
@@ -32,17 +32,25 @@ static inline void task_io_account_write(size_t bytes)
*/
static inline unsigned long task_io_get_oublock(const struct task_struct *p)
{
- return p->ioac.write_bytes >> 9;
+ return p->ioac.blk.write_bytes >> 9;
}

static inline void task_io_account_cancelled_write(size_t bytes)
{
- current->ioac.cancelled_write_bytes += bytes;
+ current->ioac.blk.cancelled_write_bytes += bytes;
}

-static inline void task_io_accounting_init(struct task_struct *tsk)
+static inline void task_io_accounting_init(struct proc_io_accounting *ioac)
{
- memset(&tsk->ioac, 0, sizeof(tsk->ioac));
+ memset(ioac, 0, sizeof(*ioac));
+}
+
+static inline void task_blk_io_accounting_add(struct proc_io_accounting *dst,
+ struct proc_io_accounting *src)
+{
+ dst->blk.read_bytes += src->blk.read_bytes;
+ dst->blk.write_bytes += src->blk.write_bytes;
+ dst->blk.cancelled_write_bytes += src->blk.cancelled_write_bytes;
}

#else
@@ -69,9 +77,37 @@ static inline void task_io_account_cancelled_write(size_t bytes)
{
}

-static inline void task_io_accounting_init(struct task_struct *tsk)
+static inline void task_io_accounting_init(struct proc_io_accounting *ioac)
+{
+}
+
+static inline void task_blk_io_accounting_add(struct proc_io_accounting *dst,
+ struct proc_io_accounting *src)
{
}

-#endif /* CONFIG_TASK_IO_ACCOUNTING */
-#endif /* __TASK_IO_ACCOUNTING_OPS_INCLUDED */
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+#ifdef CONFIG_TASK_XACCT
+static inline void task_chr_io_accounting_add(struct proc_io_accounting *dst,
+ struct proc_io_accounting *src)
+{
+ dst->chr.rchar += src->chr.rchar;
+ dst->chr.wchar += src->chr.wchar;
+ dst->chr.syscr += src->chr.syscr;
+ dst->chr.syscw += src->chr.syscw;
+}
+#else
+static inline void task_chr_io_accounting_add(struct proc_io_accounting *dst,
+ struct proc_io_accounting *src)
+{
+}
+#endif /* CONFIG_TASK_XACCT */
+
+static inline void task_io_accounting_add(struct proc_io_accounting *dst,
+ struct proc_io_accounting *src)
+{
+ task_chr_io_accounting_add(dst, src);
+ task_blk_io_accounting_add(dst, src);
+}
+#endif /* __TASK_IO_ACCOUNTING_OPS_INCLUDED */
diff --git a/kernel/exit.c b/kernel/exit.c
index 0caf590..eb4d647 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -121,18 +121,7 @@ static void __exit_signal(struct task_struct *tsk)
sig->nivcsw += tsk->nivcsw;
sig->inblock += task_io_get_inblock(tsk);
sig->oublock += task_io_get_oublock(tsk);
-#ifdef CONFIG_TASK_XACCT
- sig->rchar += tsk->rchar;
- sig->wchar += tsk->wchar;
- sig->syscr += tsk->syscr;
- sig->syscw += tsk->syscw;
-#endif /* CONFIG_TASK_XACCT */
-#ifdef CONFIG_TASK_IO_ACCOUNTING
- sig->ioac.read_bytes += tsk->ioac.read_bytes;
- sig->ioac.write_bytes += tsk->ioac.write_bytes;
- sig->ioac.cancelled_write_bytes +=
- tsk->ioac.cancelled_write_bytes;
-#endif /* CONFIG_TASK_IO_ACCOUNTING */
+ task_io_accounting_add(&sig->ioac, &tsk->ioac);
sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
sig = NULL; /* Marker for below. */
}
@@ -1363,21 +1352,8 @@ static int wait_task_zombie(struct task_struct *p, int options,
psig->coublock +=
task_io_get_oublock(p) +
sig->oublock + sig->coublock;
-#ifdef CONFIG_TASK_XACCT
- psig->rchar += p->rchar + sig->rchar;
- psig->wchar += p->wchar + sig->wchar;
- psig->syscr += p->syscr + sig->syscr;
- psig->syscw += p->syscw + sig->syscw;
-#endif /* CONFIG_TASK_XACCT */
-#ifdef CONFIG_TASK_IO_ACCOUNTING
- psig->ioac.read_bytes +=
- p->ioac.read_bytes + sig->ioac.read_bytes;
- psig->ioac.write_bytes +=
- p->ioac.write_bytes + sig->ioac.write_bytes;
- psig->ioac.cancelled_write_bytes +=
- p->ioac.cancelled_write_bytes +
- sig->ioac.cancelled_write_bytes;
-#endif /* CONFIG_TASK_IO_ACCOUNTING */
+ task_io_accounting_add(&psig->ioac, &p->ioac);
+ task_io_accounting_add(&psig->ioac, &sig->ioac);
spin_unlock_irq(&p->parent->sighand->siglock);
}

diff --git a/kernel/fork.c b/kernel/fork.c
index 5e050c1..8214ba7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -806,12 +806,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
-#ifdef CONFIG_TASK_XACCT
- sig->rchar = sig->wchar = sig->syscr = sig->syscw = 0;
-#endif
-#ifdef CONFIG_TASK_IO_ACCOUNTING
- memset(&sig->ioac, 0, sizeof(sig->ioac));
-#endif
+ task_io_accounting_init(&sig->ioac);
sig->sum_sched_runtime = 0;
INIT_LIST_HEAD(&sig->cpu_timers[0]);
INIT_LIST_HEAD(&sig->cpu_timers[1]);
@@ -994,13 +989,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->last_switch_timestamp = 0;
#endif

-#ifdef CONFIG_TASK_XACCT
- p->rchar = 0; /* I/O counter: bytes read */
- p->wchar = 0; /* I/O counter: bytes written */
- p->syscr = 0; /* I/O counter: read syscalls */
- p->syscw = 0; /* I/O counter: write syscalls */
-#endif
- task_io_accounting_init(p);
+ task_io_accounting_init(&p->ioac);
acct_clear_integrals(p);

p->it_virt_expires = cputime_zero;
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 3da47cc..f9cd256 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -94,14 +94,14 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
stats->hiwater_vm = mm->hiwater_vm * PAGE_SIZE / KB;
mmput(mm);
}
- stats->read_char = p->rchar;
- stats->write_char = p->wchar;
- stats->read_syscalls = p->syscr;
- stats->write_syscalls = p->syscw;
+ stats->read_char = p->ioac.chr.rchar;
+ stats->write_char = p->ioac.chr.wchar;
+ stats->read_syscalls = p->ioac.chr.syscr;
+ stats->write_syscalls = p->ioac.chr.syscw;
#ifdef CONFIG_TASK_IO_ACCOUNTING
- stats->read_bytes = p->ioac.read_bytes;
- stats->write_bytes = p->ioac.write_bytes;
- stats->cancelled_write_bytes = p->ioac.cancelled_write_bytes;
+ stats->read_bytes = p->ioac.blk.read_bytes;
+ stats->write_bytes = p->ioac.blk.write_bytes;
+ stats->cancelled_write_bytes = p->ioac.blk.cancelled_write_bytes;
#else
stats->read_bytes = 0;
stats->write_bytes = 0;
--
1.5.4.3

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