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common/iobuf: optimize iobuf_read_line 

* common/iobuf.c (iobuf_read_line): Add fast path for finding '\n'
character in buffer.
--

This patch reduce per byte overhead in iobuf_read_line by avoiding
using iobuf_get when possible and use memchr to find '\n'. This
speeds armored decryption.

Benchmark results below, tested on Intel Core i7-4790K (turbo off).
Encrypted 2 GiB through pipe to ramfs file using AES128. Decrypt
ramfs file out through pipe to /dev/null.

before patch-set
----------------
               gpg process
armor:         user time    pipe transfer rate
 encrypt-aead:  13.8         140 MB/s
 decrypt-aead:  30.6         68 MB/s
 encrypt-cfb:   17.4         114 MB/s
 decrypt-cfb:   32.6         64 MB/s

after (decrypt+iobuf opt)
-------------------------
               gpg process
armor:         user time    pipe transfer rate
 decrypt-aead:  22.5         92 MB/s
 decrypt-cfb:   24.4         85 MB/s

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
This commit is contained in:
Jussi Kivilinna 2018-11-08 21:31:12 +02:00
parent 47424881b2
commit 2b5718c1f7
1 changed files with 43 additions and 5 deletions
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48
common/iobuf.c
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@ -2610,12 +2610,50 @@ iobuf_read_line (iobuf_t a, byte ** addr_of_buffer,
}
p = buffer;
while ((c = iobuf_get (a)) != -1)
while (1)
{
*p++ = c;
nbytes++;
if (c == '\n')
break;
if (!a->nofast && a->d.start < a->d.len && nbytes < length - 1)
/* Fast path for finding '\n' by using standard C library's optimized
memchr. */
{
unsigned size = a->d.len - a->d.start;
byte *newline_pos;
if (size > length - 1 - nbytes)
size = length - 1 - nbytes;
newline_pos = memchr (a->d.buf + a->d.start, '\n', size);
if (newline_pos)
{
/* Found newline, copy buffer and return. */
size = (newline_pos - (a->d.buf + a->d.start)) + 1;
memcpy (p, a->d.buf + a->d.start, size);
p += size;
nbytes += size;
a->d.start += size;
a->nbytes += size;
break;
}
else
{
/* No newline, copy buffer and continue. */
memcpy (p, a->d.buf + a->d.start, size);
p += size;
nbytes += size;
a->d.start += size;
a->nbytes += size;
}
}
else
{
c = iobuf_readbyte (a);
if (c == -1)
break;
*p++ = c;
nbytes++;
if (c == '\n')
break;
}
if (nbytes == length - 1)
/* We don't have enough space to add a \n and a \0. Increase