> -----Original Message----- > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com] > Sent: Monday, November 3, 2014 4:59 PM > To: Zhang, Helin > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v5 1/5] i40e: Use constant random hash keys > > 2014-11-03 08:18, Zhang, Helin: > > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com] > > > The title is a bit surprising: > > > - it should be about RSS > > > > RSS makes use of hash function to route received packets, though hash > > function can be used for other cases, e.g. Flow director. > > Yes but this patch is only changing rss_key_default so I guess it's only > related to > RSS, right? Yes, it is currently for rss only.
> > > > - a constant cannot be really random ;) The comments could be re-worded. > > > > The hash keys are generated by libc random function. > > It is preparatory to avoid calling random function for each port. > > Here, you remove the call to rte_rand by a constant value. No need to calculate it every time, like what Linux i40e driver does. > > > > 2014-10-21 11:14, Helin Zhang: > > > > To be simpler, and remove the race condition, it uses prepared > > > > constant random hash keys to replace runtime generating the hash keys. > > > > > > Could you explain what is the role of rss_key_default? > > > > Hash function needs to be configured with keys, before end users > > configured them with specific keys, we need to provide a default keys > > which is generated by libc random function. > > The random keys can get the hash function to route the received > > packets to all the queues well-proportioned. Regards, Helin
