Hi Olivier, > -----Original Message----- > From: Olivier MATZ [mailto:olivier.m...@6wind.com] > Sent: Tuesday, February 21, 2017 9:54 AM > To: Ananyev, Konstantin <konstantin.anan...@intel.com> > Cc: Olivier Matz <olivier.m...@6wind.com>; Jan Blunck > <jblu...@infradead.org>; dev@dpdk.org > Subject: Re: [dpdk-dev] [RFC 0/8] mbuf: structure reorganization > > Hi Konstantin, > > On Fri, 17 Feb 2017 18:42:01 +0000, "Ananyev, Konstantin" > <konstantin.anan...@intel.com> wrote: > > Hi guys, > > > > > > My point is that I still doubt that it belongs into the first > > > > cacheline. It requires accessing other structures for converting > > > > into nanoseconds anyway. Optimally I would like to see this > > > > happening on access instead but if that isn't achievable at least > > > > in a second step. > > > > > > Sorry, I don't really get your point. My comprehension of the > > > timestamp usage in a PMD is as following: > > > > > > rx_burst(struct rxq *rxq, ...) > > > { > > > unsigned long factor = rxq->timestamp_factor; > > > unsigned port = rxq->port; > > > > > > for each hw_desc { > > > m = rte_pktmbuf_alloc(rxq->pool); > > > m->len = hw_desc->len; > > > m->port = port; > > > m->ol_flags = > > > ... > > > m->timestamp = hw_desc->timestamp * factor; > > > } > > > ... > > > } > > > > > > In that case, I think it deserves to be in the 1st cache line. > > > > So you are saying that: > > - for some HW that DPDK supports (mlx?) timestamp information > > Is available in HW RX descriptor > > - and as soon timestamp field will be available in mbuf, you plan > > to populate it using this HW RXD field. > > Is that so? > > Yes, that's what I'm seeing in mellanox's patchset: > http://dpdk.org/ml/archives/dev/2016-October/048810.html
Have to admit that I saw that patch before, but missed the fact that timestamp value is taken from HW RXD. Ok, then I suppose I don't' have any good reason to object against putting it in the first cache-line. > > Do you know if Intel has plans to support some sort of timestamp using > this timestamp field? > As I remember, metrics library uses it, but right now it is filled by SW. Konstantin
