netdev - RE: [net-next PATCH 2/3] net: fix enforcing of fragment queue hash list depth

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Date:	Fri, 19 Apr 2013 04:14:50 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Jesper Dangaard Brouer <brouer@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org
Subject: RE: [net-next PATCH 2/3] net: fix enforcing of fragment queue hash
 list depth

On Fri, 2013-04-19 at 11:41 +0100, David Laight wrote:
> > The 64 slots hash table was chosen years ago, when machines had 3 order
> > of magnitude less ram than today.
> > 
> > Before hash resizing, I would just bump hash size to something more
> > reasonable like 1024.
> 
> While that is true of many systems, there are embedded systems
> with much less ram than the typical x86 desktop or server.
> 
> There seem to be quite a lot of large hash tables appearing
> that on many small systems will never contain a significant
> number of entries and just waste precious memory.

Embedded systems run linux since ages, and their memory also increased
by 2 order of magnitude since 1995.

If they run linux-3.10, using 4096 bytes of 8192 bytes for the hash
table is fine.

We are not going to add yet another ifdef, for such a small amount of
ram.

The code that we will add to do the resize will be larger than this.



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