Commit 0e3dc019 authored by Andrei Vagin's avatar Andrei Vagin Committed by Linus Torvalds
Browse files

procfs: add seq_put_hex_ll to speed up /proc/pid/maps 

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

[avagin@openvz.org: use unsigned int instead of int where it is suitable]
  Link: http://lkml.kernel.org/r/20180214025619.4005-1-avagin@openvz.org
[avagin@openvz.org: v2]
  Link: http://lkml.kernel.org/r/20180117082050.25406-1-avagin@openvz.org
Link: http://lkml.kernel.org/r/20180112185812.7710-1-avagin@openvz.org


Signed-off-by: default avatarAndrei Vagin <avagin@openvz.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 69ca372c

fs/proc/task_mmu.c

+12 −9
Original line number Diff line number Diff line
@@ -287,15 +287,18 @@ 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

fs/seq_file.c

+46 −0
Original line number Diff line number Diff line
@@ -715,6 +715,52 @@ overflow: 
}

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, "%08llx", 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, unsigned int width)

{

	unsigned int len;

	int i;



	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;

include/linux/seq_file.h

+3 −0
Original line number Diff line number Diff line
@@ -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, unsigned 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,

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