On 11/06/2015 04:25, "Flavio Leitner" <f...@sysclose.org> wrote:
>On Wed, Jun 10, 2015 at 03:13:21PM +0000, Daniele Di Proietto wrote:
>>
>>
>> On 10/06/2015 12:48, "Gray, Mark D" <mark.d.g...@intel.com> wrote:
>> >
>> >The vhost port won't generate an RSS hash because it is a virtual NIC.
>> >
>> >>
>> >
>> >> It doesn't cause a problem, just make the pkt fall into a slow path,
>> >>should we
>> >
>> >> fix it?
>>
>> Thanks for investigating this. We should definitely fix it.
>>
>> >
>> >> The flag ol_flags may be useful for OVS or let DPDK fix this in vhost
>> >>rcv.
>> >
>> >
>> >
>> >How do you propose that this would work? The RSS would still have to be
>> >
>> >generated in software.
>> >
>> >>
>>
>> A simple solution would be to reset the RSS hash inside
>> netdev_dpdk_vhost_rxq_recv(). Other netdev providers that do not
>>support
>> reading the RSS hash (netdev-linux, netdev-bsd) call
>> dp_packet_set_rss_hash(pkt, 0) on every received packet.
>>
>> This would probably have a small impact on performance, but it's better
>> than trashing the exact match cache.
>>
>> I don't believe there's anything that DPDK can do here (like resetting
>>the
>> hash when the packet is freed), but please correct me if I'm wrong.
>>
>> Thoughts?
>
>I think Dongjun is right and we should use ol_flags.
>Something like this:
>
>diff --git a/lib/dp-packet.h b/lib/dp-packet.h
>index e4c2593..ad315d1 100644
>--- a/lib/dp-packet.h
>+++ b/lib/dp-packet.h
>@@ -518,7 +518,12 @@ static inline uint32_t
> dp_packet_get_rss_hash(struct dp_packet *p)
> {
> #ifdef DPDK_NETDEV
>- return p->mbuf.hash.rss;
>+ if (p->mbuf.ol_flags & PKT_RX_RSS_HASH) {
>+ return p->mbuf.hash.rss;
>+ }
>+ else {
>+ return 0;
>+ }
> #else
> return p->rss_hash;
> #endif
>
>
>I haven't tested that but rte_vhost_dequeue_burst() does
>ol_flags = 0, so this would be a generic solution for all
>dpdk devices.
>
>Thoughts?
>
>fbl
This seems a much better solution. I had no idea that ol_flags
included PKT_RX_RSS_HASH.
Unfortunately, I tested it and it appears that ixgbe_recv_pkts_vec()
is not setting the flag correctly (it is documented in the comments).
Other ideas?
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