netdev - Re: stmmac: turn coalescing / NAPI off in stmmac

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Message-ID: <20161202104238.GA31172@amd>
Date:   Fri, 2 Dec 2016 11:42:38 +0100
From:   Pavel Machek <pavel@....cz>
To:     Giuseppe CAVALLARO <peppe.cavallaro@...com>
Cc:     David Miller <davem@...emloft.net>, alexandre.torgue@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: stmmac: turn coalescing / NAPI off in stmmac

Hi!

> >Anyway... since you asked. I belive I have way to disable NAPI / tx
> >coalescing in the driver. Unfortunately, locking is missing on the rx
> >path, and needs to be extended to _irqsave variant on tx path.
> 
> I have just replied to a previous thread about that...

Yeah, please reply to David's mail where he describes why it can't
work.

> >So patch currently looks like this (hand edited, can't be
> >applied, got it working few hours ago). Does it look acceptable?
> >
> >I'd prefer this to go after the patch that pulls common code to single
> >place, so that single place needs to be patched. Plus I guess I should
> >add ifdefs, so that more advanced NAPI / tx coalescing code can be
> >reactivated when it is fixed. Trivial fixes can go on top. Does that
> >sound like a plan?
> 
> Hmm, what I find strange is that, just this code is running since a
> long time on several platforms and Chip versions. No raise condition
> have been found or lock protection problems (also proving look
> mechanisms).

Well, it works better for me when I disable CONFIG_SMP. It is normal
that locking problems are hard to reproduce :-(.

> Pavel, I ask you sorry if I missed some problems so, if you can
> (as D. Miller asked) to send us a cover letter + all patches
> I will try to reply soon. I can do also some tests if you ask
> me that! I could run on 3.x and 4.x but I cannot promise you
> benchmarks.

Actually... I have questions here. David normally pulls from you (can
I have a address of your git tree?).

Could you apply these to your git?

[PATCH] stmmac ethernet: unify locking
[PATCH] stmmac: simplify flag assignment
[PATCH] stmmac: cleanup documenation, make it match reality

They are rather trivial and independend, I'm not sure what cover
letter would say, besides "simple fixes".

Then I can re-do the reset on top of that...

> >Which tree do you want patches against?
> >
> >https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/ ?
> 
> I think that bug fixing should be on top of net.git but I let Miller
> to decide.

Hmm. It is "only" a performance problem (40msec delays).. I guess
-next is better target.

Best regards,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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