[spp] (x-fn-spp-ml 796) Re: (x-fn-spp-ml 783) Re: [PATCH 5/5] docs: add note regarding NUMA configuration

[Hideyuki Yamashita]

Hello, 

Thanks for your comments.
Please see inline.

> > Hi.
> > Sorry for delayed response.
> > Please see my comments inline.
> >
> >>> From: Hideyuki Yamashita <yamashita.hideyuki at ntt-tx.co.jp>
> >>>
> >>> This patch adds new notes for NUMA configuration when starting
> >>> spp_primary.
> >>>
> >>> This is pointed out by the following DPDK Bugzilla tickets.
> >>> https://bugs.dpdk.org/show_bug.cgi?id=457
> >>>
> >>> Signed-off-by: Hideyuki Yamashita <yamashita.hideyuki at ntt-tx.co.jp>
> >>> Signed-off-by: Naoki Takada <ntakada14 at gmail.com>
> >>> ---
> >>>    docs/guides/gsg/howto_use.rst | 12 ++++++++++++
> >>>    1 file changed, 12 insertions(+)
> >>>
> >>> diff --git a/docs/guides/gsg/howto_use.rst b/docs/guides/gsg/howto_use.rst
> >>> index f182198..4f2e6cd 100644
> >>> --- a/docs/guides/gsg/howto_use.rst
> >>> +++ b/docs/guides/gsg/howto_use.rst
> >>> @@ -422,6 +422,18 @@ if you run the process on single NUMA node.
> >>>       If you use DPDK v18.11 or later, ``--base-virtaddr 0x100000000`` is enabled
> >>>       in default. You need to use this option only for changing the default value.
> >>>   > +.. note::
> >>> +
> >>> +   ``spp_primary`` tries to create memory pool in the same NUMA node where
> >>> +   it is launched. Under NUMA configuration, the NUMA node where ``spp_primary``
> >>> +   is launched and the NUMA node where NIC is connected can be different
> >>> +   (e.g. spp_primary runs in NUMA node 0 while NIC is connected with NUMA
> >>> +   node 1).
> >>> +   Such configuration may cause performance degradation. In general, under
> >>> +   NUMA configuration, it is best practice to use CPU and NIC which belongs
> >>> +   to the same NUMA node for best performance. So user should align those
> >>> +   when performance degradation makes the situation critical.
> >>> +
> >> I have two comments.
> >>
> >> 1. Could I confirm WHAT should be configured for avoiding such a performance loss?
> >
> > NUMA node
> > - primary process will run (that can be specified with -l parameter)
> > - NIC belongs
> > should be the same to avoid performance loss.
> >
> > In general, topology regarding with NUMA node
> > (e.g. CPU core, NIC which is connected with specific NUMA node)
> > can be found in lstopo command.
> I would like to make it clear as an instruction for users. From my understanding, users should confirm that
> - Understand layout of hardware architecture of NICs and CPUs.
> - Assign lcores while launching spp_primary by considering the layout identified before.
> 
> I understand your update for explanation is collect, but not so clear the purpose as instruction.
>I think it could be more agreeable if you start to explaining WHAT can
>be happened if you do not care about the layout (performance
>degradation actually), then HOW you get the layout by using `lstopo`
>and HOW you configure lcores by using `-l` option.

OK.
I think in general we can agree on the concept of the change.
I think it might be better that 
- I add description in the "Performance Optimization" section because it
is highly related with "Performance"!
- Firstly I should explain "what will happen" if such consideration
   is NOT taken into account by users
- Secondary I should describe "how" users can avoid such
performance degradations (e.g. use lstopo command, specify appropriate
lcore when starting up spp_primary process)

Anyway I think it is better to discuss above over "actual" changes.

Thanks
I will send revised version of the patch when it got available.

BR,
Hideyuki Yamashita

> Thanks,
> Yasufumi
> 
> >
> >
> >> 2. It seems something abruptly considering context of this section because you start talking about performance suddenly.
> >> If it must be considered as a mandatory configuration and should be explained this section, I agree your update.
> >> On the other hand, what do you think to move this note to the next "Performance Optimization" section.
> >> I think no need to be a note if you move it to the next secion.
> >
> > I agree with your idea.
> > I think it is NOT mandatory, thus should be moved to next section
> > 'without' note.
> >
> >>
> >> Thanks
> >>
> >>>    If ``spp_primary`` is launched with two or more lcores, forwarder or monitor
> >>>    is activated. The default is forwarder and monitor is optional in this case.
> >>>    If you use monitor thread, additional option ``--disp-stat`` is required.
> >
> >