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>
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@ -22,17 +22,22 @@
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uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
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uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
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{
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{
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uint32_t sum = 0;
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uint32_t sum1 = 0, sum2 = 0;
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int i;
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int i;
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for (i = seq; i < seq + len; i++) {
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for (i = 0; i < len - 1; i += 2) {
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if (i & 1) {
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sum1 += (uint32_t)buf[i];
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sum += (uint32_t)buf[i - seq];
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sum2 += (uint32_t)buf[i + 1];
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} else {
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}
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sum += (uint32_t)buf[i - seq] << 8;
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if (i < len) {
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}
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sum1 += (uint32_t)buf[i];
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}
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if (seq & 1) {
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return sum1 + (sum2 << 8);
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} else {
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return sum2 + (sum1 << 8);
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}
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}
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return sum;
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}
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}
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uint16_t net_checksum_finish(uint32_t sum)
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uint16_t net_checksum_finish(uint32_t sum)
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