netdev - Re: [PATCH net-next 2/2] bnx2x: use the default NAPI weight

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Date:	Tue, 05 Mar 2013 23:37:44 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, eilong@...adcom.com
Subject: Re: [PATCH net-next 2/2] bnx2x: use the default NAPI weight

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 05 Mar 2013 19:28:29 -0800

> We are facing a fanout/fanin problem for a given application.
> 
> What happens is that link is mostly idle, and every couple of minutes,
> we receive a burst of messages, needing a burst of transmits.
> 
> BQL starts with a limit of 0, meaning it needs some TX completion runs
> to be able to detect the sudden increase of TX need and reach line rate.
> 
> bnx2x is really unfair in this scenario, because the NAPI poll budget is
> very high, and aggregated packets (by LRO) count for a single packet in
> the budget. (or even 0, see the "goto next_cqe;" that avoids the rx_pkt
> ++; in drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c line 1007)
> 
> We probably have other issues in the stack, I am patiently finding all
> of them. In the mean time we had to disable BQL :(

Thanks for the explanation.

Since you haven't completely resolved the issues you were running into
I'll target this to net-next for now.

Thanks!
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