On Fri, Jan 12, 2018 at 05:35:31PM +0000, Bhanuprakash Bodireddy wrote:
> pkt_metadata_prefetch_init() is used to prefetch the packet metadata
> before initializing the metadata in pkt_metadata_init(). This is done
> for every packet in userspace datapath and is performance critical.
>
> Commit 99fc16c0 prefetches only cachline0 and cacheline2 as the metadata
> part of respective cachelines will be initialized by pkt_metadata_init().
>
> However in VXLAN case when popping the vxlan header, netdev_vxlan_pop_header()
> invokes pkt_metadata_init_tnl() which zeroes out metadata part of
> cacheline1 that wasn't prefetched earlier and causes performance
> degradation.
>
> By prefetching cacheline1, 9% performance improvement is observed with
> vxlan decapsulation test case for packet sizes of 118 bytes. Performance
> variation is observed based on CFLAGS.
>
> CFLAGS="-O2" CFLAGS="-O2 -msse4.2"
> Master 4.667 Mpps Master 4.710 Mpps
> With Patch 5.045 Mpps With Patch 5.097 Mpps
>
> CFLAGS="-O2 -march=native" CFLAGS="-Ofast -march=native"
> Master 5.072 Mpps Master 5.349 Mpps
> With Patch 5.193 Mpps With Patch 5.378 Mpps
>
> Fixes: 99fc16c0 ("Reorganize the pkt_metadata structure.")
> Signed-off-by: Bhanuprakash Bodireddy <[email protected]>
> Acked by: Sugesh Chandran <[email protected]>
> ---
> v2->v3
> * Added Ack from Sugesh.
>
> v2->v1
> * Include the throughput stats with different CFLAG options.
Well, that's an easy way to boost performance.
On the basis of the ack and the performance numbers, I applied this to
master.
Thank you!
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