seq_put_hex_ll() prints a number in hexadecimal notation and works
faster than seq_printf().
== test.py
num = 0
with open("/proc/1/maps") as f:
while num < 10000 :
data = f.read()
f.seek(0, 0)
num = num + 1
==
== Before patch ==
$ time python test.py
real 0m1.561s
user 0m0.257s
sys 0m1.302s
== After patch ==
$ time python test.py
real 0m0.986s
user 0m0.279s
sys 0m0.707s
$ perf -g record python test.py:
== Before patch ==
- 67.42% 2.82% python [kernel.kallsyms] [k] show_map_vma.isra.22
- 64.60% show_map_vma.isra.22
- 44.98% seq_printf
- seq_vprintf
- vsnprintf
+ 14.85% number
+ 12.22% format_decode
5.56% memcpy_erms
+ 15.06% seq_path
+ 4.42% seq_pad
+ 2.45% __GI___libc_read
== After patch ==
- 47.35% 3.38% python [kernel.kallsyms] [k] show_map_vma.isra.23
- 43.97% show_map_vma.isra.23
+ 20.84% seq_path
- 15.73% show_vma_header_prefix
10.55% seq_put_hex_ll
+ 2.65% seq_put_decimal_ull
0.95% seq_putc
+ 6.96% seq_pad
+ 2.94% __GI___libc_read
v2: don't create a separate function to print delimiter and a few fixes
to make code more readable.
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
---
fs/proc/task_mmu.c | 21 ++++++++++++---------
fs/seq_file.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/seq_file.h | 3 +++
3 files changed, 60 insertions(+), 9 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 339e4c1c044d..3a08685ef27c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -282,15 +282,18 @@ static void show_vma_header_prefix(struct seq_file *m,
dev_t dev, unsigned long ino)
{
seq_setwidth(m, 25 + sizeof(void *) * 6 - 1);
- seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
- start,
- end,
- flags & VM_READ ? 'r' : '-',
- flags & VM_WRITE ? 'w' : '-',
- flags & VM_EXEC ? 'x' : '-',
- flags & VM_MAYSHARE ? 's' : 'p',
- pgoff,
- MAJOR(dev), MINOR(dev), ino);
+ seq_put_hex_ll(m, NULL, start, 8);
+ seq_put_hex_ll(m, "-", end, 8);
+ seq_putc(m, ' ');
+ seq_putc(m, flags & VM_READ ? 'r' : '-');
+ seq_putc(m, flags & VM_WRITE ? 'w' : '-');
+ seq_putc(m, flags & VM_EXEC ? 'x' : '-');
+ seq_putc(m, flags & VM_MAYSHARE ? 's' : 'p');
+ seq_put_hex_ll(m, " ", pgoff, 8);
+ seq_put_hex_ll(m, " ", MAJOR(dev), 2);
+ seq_put_hex_ll(m, ":", MINOR(dev), 2);
+ seq_put_decimal_ull(m, " ", ino);
+ seq_putc(m, ' ');
}
static void
diff --git a/fs/seq_file.c b/fs/seq_file.c
index bce089cc1771..d2885220ecf7 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -712,6 +712,51 @@ void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,
}
EXPORT_SYMBOL(seq_put_decimal_ull);
+/**
+ * seq_put_hex_ll - put a number in hexadecimal notation
+ * @m: seq_file identifying the buffer to which data should be written
+ * @delimiter: a string which is printed before the number
+ * @v: the number
+ * @width: a minimum field width
+ *
+ * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "0x08llx", v)
+ *
+ * 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.
+ */
+void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
+ unsigned long long v, int width)
+{
+ int i, len;
+
+ if (delimiter && delimiter[0]) {
+ if (delimiter[1] == 0)
+ seq_putc(m, delimiter[0]);
+ else
+ seq_puts(m, delimiter);
+ }
+
+ /* If x is 0, the result of __builtin_clzll is undefined */
+ if (v == 0)
+ len = 1;
+ else
+ len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
+
+ if (len < width)
+ len = width;
+
+ if (m->count + len > m->size) {
+ seq_set_overflow(m);
+ return;
+ }
+
+ for (i = len - 1; i >= 0; i--) {
+ m->buf[m->count + i] = hex_asc[0xf & v];
+ v = v >> 4;
+ }
+ m->count += len;
+}
+
void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num)
{
int len;
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 09c6e28746f9..53f238934d7f 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -121,6 +121,9 @@ void seq_puts(struct seq_file *m, const char *s);
void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,
unsigned long long num);
void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num);
+void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
+ unsigned long long v, int width);
+
void seq_escape(struct seq_file *m, const char *s, const char *esc);
void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
--
2.13.6
