Re: [dpdk-dev] [dpdk-stable] [PATCH] app/testpmd: fix txonly flow generation entropy

[Slava Ovsiienko <viacheslavo@mellanox.com>]

Hi, Ferruh

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Monday, February 10, 2020 16:02
> To: Slava Ovsiienko <viacheslavo@mellanox.com>; dev@dpdk.org
> Cc: Thomas Monjalon <thomas@monjalon.net>;
> bernard.iremonger@intel.com; stable@dpdk.org
> Subject: Re: [dpdk-stable] [PATCH] app/testpmd: fix txonly flow generation
> entropy
> 
> On 2/9/2020 5:02 PM, Viacheslav Ovsiienko wrote:
> > The testpmd application in txonly forwarding mode has an option to
> > generate the packet flows by varying the destination IP address.
> > The patch increments the IP for each packet sent, this improves the
> > entropy and RSS distibution on the peer receiving size is getting more
> > uniform.
> 
> The IP address already incremented for each packet sent [1], I can't see what
> this patch adds.

Not exactly, that commit increments the ip_var local variable only.
On the next call ip_var is assigned from thread local storage variable
ip_var = RTE_PER_LCORE(_ip_var) - and increment is lost, it is supposed to be a bug.
We have the bursts of packets with the same IPs.

My patch stores the incremented value in the local storage  variable.  It is double checked,
after applying the patch we see the more fair RSS distribution on receiving peer.

With best regards, Slava

> 
> [1]
> https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Flxr.dpdk.
> org%2Fdpdk%2Fv19.11%2Fsource%2Fapp%2Ftest-
> pmd%2Ftxonly.c%23L208&amp;data=02%7C01%7Cviacheslavo%40mellanox.co
> m%7C6a5be2d6ecdd4c487e7908d7ae31dc95%7Ca652971c7d2e4d9ba6a4d149
> 256f461b%7C0%7C0%7C637169401491712071&amp;sdata=QMXvKlSVy3vAUMz
> Fzj%2ByRKKWUcVToR3hlX8S3a7V21I%3D&amp;reserved=0
> 
> 
> btw, for reference the option mentioned is "--txonly-multi-flow" and it has
> been added with:
> commit: 82010ef55e7c ("app/testpmd: make txonly mode generate multiple
> flows")
> 
Mmm, yes. My patch refers exactly to the this. Sorry, I do not understand your comment,
could you, please, clarify what do you mean?

With best regards, Slava