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vsprintf: rework bitmap_list_string

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bitmap_list_string() is very ineffective when printing bitmaps with long
ranges of set bits because it calls find_next_bit for each bit in the
bitmap.  We can do better by detecting ranges of set bits.

In my environment, before/after is 943008/31008 ns.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
This commit is contained in:
Yury Norov 2021-08-14 14:17:13 -07:00
parent db7313005e
commit 15325b4f76
1 changed files with 7 additions and 17 deletions
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24
lib/vsprintf.c
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@ -1241,20 +1241,13 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
struct printf_spec spec, const char *fmt)
{
int nr_bits = max_t(int, spec.field_width, 0);
/* current bit is 'cur', most recently seen range is [rbot, rtop] */
int cur, rbot, rtop;
bool first = true;
int rbot, rtop;
if (check_pointer(&buf, end, bitmap, spec))
return buf;
rbot = cur = find_first_bit(bitmap, nr_bits);
while (cur < nr_bits) {
rtop = cur;
cur = find_next_bit(bitmap, nr_bits, cur + 1);
if (cur < nr_bits && cur <= rtop + 1)
continue;
for_each_set_bitrange(rbot, rtop, bitmap, nr_bits) {
if (!first) {
if (buf < end)
*buf = ',';
@ -1263,15 +1256,12 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
first = false;
buf = number(buf, end, rbot, default_dec_spec);
if (rbot < rtop) {
if (buf < end)
*buf = '-';
buf++;
if (rtop == rbot + 1)
continue;
buf = number(buf, end, rtop, default_dec_spec);
}
rbot = cur;
if (buf < end)
*buf = '-';
buf = number(++buf, end, rtop - 1, default_dec_spec);
}
return buf;
}