Re: [net-next PATCH 3/3] qlge: Increase default TX/RX ring size to 1024.

[Stephen Hemminger <shemminger@vyatta.com>]

On Thu, 11 Jun 2009 02:27:13 -0700 (PDT)
David Miller <davem@davemloft.net> wrote:

> From: Ron Mercer <ron.mercer@qlogic.com>
> Date: Wed, 10 Jun 2009 18:49:35 -0700
> 
> > 
> > Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
> 
> This is huge.  Even other aggressive NICs such as BNX2X only use 256
> ring entries per TX queue.
> 
> There is a point where increasing definitely hurts, because you're
> increasing the resident set size of the cpu, as more and more SKBs are
> effectively "in flight" at a given time and only due to the amount
> you're allowing to get queued up into the chip.
> 
> And with multiqueue, per-queue TX queue sizes should matter less at
> least to some extent.
> 
> Are you sure that jacking the value up this high has no negative side
> effects for various workloads?

I am investigating reducing the sky2 default tx ring size down to
128 after user complaints about the latency. At 10G 1024 ring
entries is 7ms for jumbo frames.