linux-kernel - RE: RFC: memory leak in udp_table

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Date:	Mon, 27 Feb 2012 11:33:07 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Eric Dumazet" <eric.dumazet@...il.com>,
	"David Miller" <davem@...emloft.net>
Cc:	<paul.gortmaker@...driver.com>, <tim.bird@...sony.com>,
	<kuznet@....inr.ac.ru>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>
Subject: RE: RFC: memory leak in udp_table_init

> > > [PATCH] mm: add a low limit to alloc_large_system_hash
> > 
> > I think you should just use zero as the default minimum for all
> > call sites except this UDP case we are trying to fix.
> > 
> > For example I see you used 16 for kernel/pid.c
> > 
> > Let's not try to do unrelated changes like that now, we can do such
> > tweaks later.
> 
> It was to match the comment we have few lines above :
> 
> /*
>  * The pid hash table is scaled according to the amount of memory in
the
>  * machine.  From a minimum of 16 slots up to 4096 slots at one
gigabyte or
>  * more.
>  */

These large hash tables are, IMHO, an indication that the
algorithm used is, perhaps, suboptimal.

Not least of the problems is actually finding a suitable
(and fast) hash function that will work with the actual
real-life data.

The pid table is a good example of something where a hash
table is unnecessary.
Linux should steal the code I put into NetBSD :-)

	David


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