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authorAndrei Vagin <avagin@openvz.org>2018-04-10 16:30:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-11 10:28:32 -0700
commit0e3dc019143104a6e676287b1e453cccd7add404 (patch)
treeb3aa6e165b872e86fdf5be2fe113adae58e2ee6e /fs/seq_file.c
parent69ca372c100fba99c78ef826a1795aa86e4f01a8 (diff)
downloadlinux-stericsson-0e3dc019143104a6e676287b1e453cccd7add404.tar.gz
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: Andrei Vagin <avagin@openvz.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/seq_file.c')
-rw-r--r--fs/seq_file.c46
1 files changed, 46 insertions, 0 deletions
diff --git a/fs/seq_file.c b/fs/seq_file.c
index eea09f6d8830..cde1bdbf7801 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -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;