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dpif-netdev: Prefetch next packet before miniflow_extract().

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It appears that miniflow_extract() in emc_processing() spends a lot of
cycles waiting for the packet's data to be read.

Prefetching the next packet's data while parsing removes this delay.
For a single flow pipeline the throughput improves by ~10%.  With a
more realistic pipeline the change has a much smaller effect (~0.5%
improvement)

Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>
Signed-off-by: Ethan Jackson <ethan@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>
This commit is contained in:
Daniele Di Proietto
2015-06-15 19:06:39 +01:00
committed by Ethan Jackson
parent 9fc789b906
commit 72a5e2b8fc
1 changed files with 5 additions and 0 deletions
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5
lib/dpif-netdev.c
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@@ -3150,6 +3150,11 @@ emc_processing(struct dp_netdev_pmd_thread *pmd, struct dp_packet **packets,
continue;
}
if (i != cnt - 1) {
/* Prefetch next packet data */
OVS_PREFETCH(dp_packet_data(packets[i+1]));
}
miniflow_extract(packets[i], &key.mf);
key.len = 0; /* Not computed yet. */
key.hash = dpif_netdev_packet_get_rss_hash(packets[i], &key.mf);