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authorLadi Prosek <lprosek@redhat.com>2017-01-06 09:08:53 +0100
committerJason Wang <jasowang@redhat.com>2017-01-20 10:36:38 +0800
commitd5aa3e6e0cd6259003790769c448d4fbb5b5c810 (patch)
tree5594b798a8766fcb589c8f7a4fbd42253b7bba86 /net/checksum.c
parentd4aa431f945bbbff75129af0cd0b155f988150ba (diff)
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net: optimize checksum computation
Very simple loop optimization with a significant performance impact. Microbenchmark results, modern x86-64: buffer size | speed up ------------+--------- 1500 | 1.7x 64 | 1.5x 8 | 1.15x Microbenchmark results, POWER7: buffer size | speed up ------------+--------- 1500 | 5x 64 | 3.3x 8 | 1.13x There is a lot of room for further improvement at the expense of code complexity - aligned multibyte reads, LE/BE considerations, architecture-specific optimizations, etc. This patch still keeps things simple and readable. Signed-off-by: Ladi Prosek <lprosek@redhat.com> Reviewed-by: Dmitry Fleytman <dmitry@daynix.com> Signed-off-by: Jason Wang <jasowang@redhat.com>
Diffstat (limited to 'net/checksum.c')
-rw-r--r--net/checksum.c21
1 files changed, 13 insertions, 8 deletions
diff --git a/net/checksum.c b/net/checksum.c
index 23323b0..4da72a6 100644
--- a/net/checksum.c
+++ b/net/checksum.c
@@ -22,17 +22,22 @@
uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
{
- uint32_t sum = 0;
+ uint32_t sum1 = 0, sum2 = 0;
int i;
- for (i = seq; i < seq + len; i++) {
- if (i & 1) {
- sum += (uint32_t)buf[i - seq];
- } else {
- sum += (uint32_t)buf[i - seq] << 8;
- }
+ for (i = 0; i < len - 1; i += 2) {
+ sum1 += (uint32_t)buf[i];
+ sum2 += (uint32_t)buf[i + 1];
+ }
+ if (i < len) {
+ sum1 += (uint32_t)buf[i];
+ }
+
+ if (seq & 1) {
+ return sum1 + (sum2 << 8);
+ } else {
+ return sum2 + (sum1 << 8);
}
- return sum;
}
uint16_t net_checksum_finish(uint32_t sum)