netdev - Re: RFC limit sk_mem

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Date:	Wed, 22 May 2013 11:31:00 -0300
From:	Flavio Leitner <fbl@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: RFC limit sk_mem_quantum to 8192

On Tue, May 21, 2013 at 07:21:01PM -0700, Eric Dumazet wrote:
> On Tue, 2013-05-21 at 22:58 -0300, Flavio Leitner wrote:
> > On Tue, May 21, 2013 at 06:09:22PM -0700, Eric Dumazet wrote:
> >  
> > > Are you sure a network driver doesn't provide skb using a full page ?
> > 
> > You lost me. You're saying that today we consider a page size
> > a minimum and so if we reduce that, the skb wouldn't fit in the
> > min sk memory?
> 
> SK_MEM_QUANTUM is also used in UDP stack, thats why I am asking.

Yeah, it is. SCTP too, but for the protocol cases, the most
complex one appears to be TCP, and it doesn't seem to be a problem
to replace the minimum with something not page sized.

For the drivers, it seems to have an indirect assumption that
page size bytes is a minimum acceptable, so changing this minimum
could cause a performance issue.

Well, this define is quite old, so I am not sure if there are
other historical reasons to keep it page size. However, if the
idea of fixing SK_MEM_QUANTUM to 4k seems reasonable, I am
willing to spend more time digging into this.

Thanks!
-- 
fbl
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