procfs: add num_to_str() to speed up /proc/stat
== stat_check.py
num = 0
with open("/proc/stat") as f:
while num < 1000 :
data = f.read()
f.seek(0, 0)
num = num + 1
==
perf shows
20.39% stat_check.py [kernel.kallsyms] [k] format_decode
13.41% stat_check.py [kernel.kallsyms] [k] number
12.61% stat_check.py [kernel.kallsyms] [k] vsnprintf
10.85% stat_check.py [kernel.kallsyms] [k] memcpy
4.85% stat_check.py [kernel.kallsyms] [k] radix_tree_lookup
4.43% stat_check.py [kernel.kallsyms] [k] seq_printf
This patch removes most of calls to vsnprintf() by adding num_to_str()
and seq_print_decimal_ull(), which prints decimal numbers without rich
functions provided by printf().
On my 8cpu box.
== Before patch ==
[root@bluextal test]# time ./stat_check.py
real 0m0.150s
user 0m0.026s
sys 0m0.121s
== After patch ==
[root@bluextal test]# time ./stat_check.py
real 0m0.055s
user 0m0.022s
sys 0m0.030s
[akpm@linux-foundation.org: remove incorrect comment, use less statck in num_to_str(), move comment from .h to .c, simplify seq_put_decimal_ull()]
[andrea@betterlinux.com: avoid breaking the ABI in /proc/stat]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrea Righi <andrea@betterlinux.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Turner <pjt@google.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index ac44611..6a0c62d 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -89,18 +89,19 @@
}
sum += arch_irq_stat();
- seq_printf(p, "cpu %llu %llu %llu %llu %llu %llu %llu %llu %llu "
- "%llu\n",
- (unsigned long long)cputime64_to_clock_t(user),
- (unsigned long long)cputime64_to_clock_t(nice),
- (unsigned long long)cputime64_to_clock_t(system),
- (unsigned long long)cputime64_to_clock_t(idle),
- (unsigned long long)cputime64_to_clock_t(iowait),
- (unsigned long long)cputime64_to_clock_t(irq),
- (unsigned long long)cputime64_to_clock_t(softirq),
- (unsigned long long)cputime64_to_clock_t(steal),
- (unsigned long long)cputime64_to_clock_t(guest),
- (unsigned long long)cputime64_to_clock_t(guest_nice));
+ seq_puts(p, "cpu ");
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(user));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(nice));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(system));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(idle));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(iowait));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(irq));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(softirq));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(steal));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest_nice));
+ seq_putc(p, '\n');
+
for_each_online_cpu(i) {
/* Copy values here to work around gcc-2.95.3, gcc-2.96 */
user = kcpustat_cpu(i).cpustat[CPUTIME_USER];
@@ -113,26 +114,24 @@
steal = kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
guest = kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
guest_nice = kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
- seq_printf(p,
- "cpu%d %llu %llu %llu %llu %llu %llu %llu %llu %llu "
- "%llu\n",
- i,
- (unsigned long long)cputime64_to_clock_t(user),
- (unsigned long long)cputime64_to_clock_t(nice),
- (unsigned long long)cputime64_to_clock_t(system),
- (unsigned long long)cputime64_to_clock_t(idle),
- (unsigned long long)cputime64_to_clock_t(iowait),
- (unsigned long long)cputime64_to_clock_t(irq),
- (unsigned long long)cputime64_to_clock_t(softirq),
- (unsigned long long)cputime64_to_clock_t(steal),
- (unsigned long long)cputime64_to_clock_t(guest),
- (unsigned long long)cputime64_to_clock_t(guest_nice));
+ seq_printf(p, "cpu%d", i);
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(user));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(nice));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(system));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(idle));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(iowait));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(irq));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(softirq));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(steal));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest));
+ seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest_nice));
+ seq_putc(p, '\n');
}
seq_printf(p, "intr %llu", (unsigned long long)sum);
/* sum again ? it could be updated? */
for_each_irq_nr(j)
- seq_printf(p, " %u", kstat_irqs(j));
+ seq_put_decimal_ull(p, ' ', kstat_irqs(j));
seq_printf(p,
"\nctxt %llu\n"
@@ -149,7 +148,7 @@
seq_printf(p, "softirq %llu", (unsigned long long)sum_softirq);
for (i = 0; i < NR_SOFTIRQS; i++)
- seq_printf(p, " %u", per_softirq_sums[i]);
+ seq_put_decimal_ull(p, ' ', per_softirq_sums[i]);
seq_putc(p, '\n');
return 0;
diff --git a/fs/seq_file.c b/fs/seq_file.c
index aa242dc..7d19816 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -644,6 +644,39 @@
}
EXPORT_SYMBOL(seq_puts);
+/*
+ * A helper routine for putting decimal numbers without rich format of printf().
+ * only 'unsigned long long' is supported.
+ * This routine will put one byte delimiter + number into seq_file.
+ * This routine is very quick when you show lots of numbers.
+ * In usual cases, it will be better to use seq_printf(). It's easier to read.
+ */
+int seq_put_decimal_ull(struct seq_file *m, char delimiter,
+ unsigned long long num)
+{
+ int len;
+
+ if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
+ goto overflow;
+
+ m->buf[m->count++] = delimiter;
+
+ if (num < 10) {
+ m->buf[m->count++] = num + '0';
+ return 0;
+ }
+
+ len = num_to_str(m->buf + m->count, m->size - m->count, num);
+ if (!len)
+ goto overflow;
+ m->count += len;
+ return 0;
+overflow:
+ m->count = m->size;
+ return -1;
+}
+EXPORT_SYMBOL(seq_put_decimal_ull);
+
/**
* seq_write - write arbitrary data to buffer
* @seq: seq_file identifying the buffer to which data should be written
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index f2085b5..3e140ad 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -312,6 +312,8 @@
#define strict_strtoull kstrtoull
#define strict_strtoll kstrtoll
+extern int num_to_str(char *buf, int size, unsigned long long num);
+
/* lib/printf utilities */
extern __printf(2, 3) int sprintf(char *buf, const char * fmt, ...);
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 44f1514..5bba42c 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -121,9 +121,10 @@
void *__seq_open_private(struct file *, const struct seq_operations *, int);
int seq_open_private(struct file *, const struct seq_operations *, int);
int seq_release_private(struct inode *, struct file *);
+int seq_put_decimal_ull(struct seq_file *m, char delimiter,
+ unsigned long long num);
#define SEQ_START_TOKEN ((void *)1)
-
/*
* Helpers for iteration over list_head-s in seq_files
*/
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 38e612e..385c402 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -212,6 +212,26 @@
}
}
+/*
+ * Convert passed number to decimal string.
+ * Returns the length of string. On buffer overflow, returns 0.
+ *
+ * If speed is not important, use snprintf(). It's easy to read the code.
+ */
+int num_to_str(char *buf, int size, unsigned long long num)
+{
+ char tmp[21]; /* Enough for 2^64 in decimal */
+ int idx, len;
+
+ len = put_dec(tmp, num) - tmp;
+
+ if (len > size)
+ return 0;
+ for (idx = 0; idx < len; ++idx)
+ buf[idx] = tmp[len - idx - 1];
+ return len;
+}
+
#define ZEROPAD 1 /* pad with zero */
#define SIGN 2 /* unsigned/signed long */
#define PLUS 4 /* show plus */