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MEDIUM: buffers: make b_xfer() automatically swap buffers when possible 

Whenever it's possible to avoid a copy, b_xfer() will simply swap the
buffer's heads without touching the data. This has brought the performance
back from 140 kH/s to 202 kH/s on the test case.
This commit is contained in:
Willy Tarreau 2018-07-20 18:58:51 +02:00
parent a56a6def91
commit 7999bfbfd3
1 changed files with 10 additions and 1 deletions
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11
include/common/buf.h
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@ -517,7 +517,9 @@ static inline size_t b_putblk(struct buffer *b, const char *blk, size_t len)
/* b_xfer() : transfers at most <count> bytes from buffer <src> to buffer <dst> /* b_xfer() : transfers at most <count> bytes from buffer <src> to buffer <dst>
* and returns the number of bytes copied. The bytes are removed from <src> and * and returns the number of bytes copied. The bytes are removed from <src> and
* added to <dst>. The caller is responsible for ensuring that <count> is not * added to <dst>. The caller is responsible for ensuring that <count> is not
* larger than b_room(dst). * larger than b_room(dst). Whenever possible (if the destination is empty and
* at least as much as the source was requested), the buffers are simply
* swapped instead of copied.
*/ */
static inline size_t b_xfer(struct buffer *dst, struct buffer *src, size_t count) static inline size_t b_xfer(struct buffer *dst, struct buffer *src, size_t count)
{ {
@ -533,6 +535,13 @@ static inline size_t b_xfer(struct buffer *dst, struct buffer *src, size_t count
if (ret > count) if (ret > count)
ret = count; ret = count;
else if (!b_data(dst)) {
/* zero copy is possible by just swapping buffers */
struct buffer tmp = *dst;
*dst = *src;
*src = tmp;
goto leave;
}
block1 = b_contig_data(src, 0); block1 = b_contig_data(src, 0);
if (block1 > ret) if (block1 > ret)