| Message ID | 1454123675-13245-2-git-send-email-azhou@ovn.org |
|---|---|
| State | Superseded |
| Headers | show |
On Fri, Jan 29, 2016 at 07:14:35PM -0800, Andy Zhou wrote: > This is essentially the same patch as the original patched posted at: > http://openvswitch.org/pipermail/dev/2016-January/064971.html > > The original commit message: > Before this commit, emc_processing() copied a netdev_flow_key if > there was no exact-match cache (EMC) hit. This commit eliminates > the copy by constructing the netdev_flow_key in the place it would > be copied. > > Found by inspection. > > Shahbaz (CCed) reports that this reduces the cost of an EMC miss by > 72 cycles in his test case in which the EMC is disabled. > Presumably this is similarly valuable in cases where the EMC merely > has few hits. > > However, the original patch introduced a slight performance drop for the > fast path, where every packets hits the emc cache. This patch removes > the performance drop by only reloading the key variable when a miss > happens. > > CC: Muhammad Shahbaz <mshahbaz@cs.princeton.edu> > Signed-off-by: Ben Pfaff <blp@ovn.org> > Sgned-off-by: Andy Zhou <azhou@ovn.org> Oops, I applied my version of this after getting your and Daniele's acks. You'll probably have to respin this series, sorry.
On Mon, Feb 1, 2016 at 11:15 AM, Ben Pfaff <blp@ovn.org> wrote: > On Fri, Jan 29, 2016 at 07:14:35PM -0800, Andy Zhou wrote: >> This is essentially the same patch as the original patched posted at: >> http://openvswitch.org/pipermail/dev/2016-January/064971.html >> >> The original commit message: >> Before this commit, emc_processing() copied a netdev_flow_key if >> there was no exact-match cache (EMC) hit. This commit eliminates >> the copy by constructing the netdev_flow_key in the place it would >> be copied. >> >> Found by inspection. >> >> Shahbaz (CCed) reports that this reduces the cost of an EMC miss by >> 72 cycles in his test case in which the EMC is disabled. >> Presumably this is similarly valuable in cases where the EMC merely >> has few hits. >> >> However, the original patch introduced a slight performance drop for the >> fast path, where every packets hits the emc cache. This patch removes >> the performance drop by only reloading the key variable when a miss >> happens. >> >> CC: Muhammad Shahbaz <mshahbaz@cs.princeton.edu> >> Signed-off-by: Ben Pfaff <blp@ovn.org> >> Sgned-off-by: Andy Zhou <azhou@ovn.org> > > Oops, I applied my version of this after getting your and Daniele's > acks. You'll probably have to respin this series, sorry. Sure. I rebased and posted a V2.
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index 205176a..94fa5ad 100644 --- a/lib/dpif-netdev.c +++ b/lib/dpif-netdev.c @@ -3297,7 +3297,7 @@ emc_processing(struct dp_netdev_pmd_thread *pmd, struct dp_packet **packets, struct packet_batch batches[], size_t *n_batches) { struct emc_cache *flow_cache = &pmd->flow_cache; - struct netdev_flow_key key; + struct netdev_flow_key *key = &keys[0]; size_t i, n_missed = 0, n_dropped = 0; for (i = 0; i < cnt; i++) { @@ -3315,19 +3315,19 @@ emc_processing(struct dp_netdev_pmd_thread *pmd, struct dp_packet **packets, OVS_PREFETCH(dp_packet_data(packets[i+1])); } - miniflow_extract(packet, &key.mf); - key.len = 0; /* Not computed yet. */ - key.hash = dpif_netdev_packet_get_rss_hash(packet, &key.mf); + miniflow_extract(packet, &key->mf); + key->len = 0; /* Not computed yet. */ + key->hash = dpif_netdev_packet_get_rss_hash(packet, &key->mf); - flow = emc_lookup(flow_cache, &key); + flow = emc_lookup(flow_cache, key); if (OVS_LIKELY(flow)) { - dp_netdev_queue_batches(packet, flow, &key.mf, batches, + dp_netdev_queue_batches(packet, flow, &key->mf, batches, n_batches); } else { /* Exact match cache missed. Group missed packets together at * the beginning of the 'packets' array. */ - packets[n_missed] = packet; - keys[n_missed++] = key; + packets[n_missed++] = packet; + key = &keys[n_missed]; } }
This is essentially the same patch as the original patched posted at: http://openvswitch.org/pipermail/dev/2016-January/064971.html The original commit message: Before this commit, emc_processing() copied a netdev_flow_key if there was no exact-match cache (EMC) hit. This commit eliminates the copy by constructing the netdev_flow_key in the place it would be copied. Found by inspection. Shahbaz (CCed) reports that this reduces the cost of an EMC miss by 72 cycles in his test case in which the EMC is disabled. Presumably this is similarly valuable in cases where the EMC merely has few hits. However, the original patch introduced a slight performance drop for the fast path, where every packets hits the emc cache. This patch removes the performance drop by only reloading the key variable when a miss happens. CC: Muhammad Shahbaz <mshahbaz@cs.princeton.edu> Signed-off-by: Ben Pfaff <blp@ovn.org> Sgned-off-by: Andy Zhou <azhou@ovn.org> --- lib/dpif-netdev.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)