Re: stmmac: turn coalescing / NAPI off in stmmac

Hi Pavel

On 12/2/2016 11:42 AM, Pavel Machek wrote:

Hi!

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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.

let me to re-check the mails :-) I can try to provide you
more details about what I experimented

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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 :-(.

can you share me the test, maybe I can try to reproduce on ARM box.
Are you using 3.x or 4.x GMAC?

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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?).

No I send the patches to the mailing list.

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...

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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.

ok, maybe if you resend these with a cover-letter I can try to
contribute on reviewing (in case of I have missed some detail).

Best Regards
Peppe

Best regards,
								Pavel