netdev - Re: [net-next PATCH V2 3/9] net: frag, move LRU list maintenance outside of rwlock

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Message-Id: <20121129.130506.329791401604974668.davem@davemloft.net>
Date:	Thu, 29 Nov 2012 13:05:06 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	brouer@...hat.com, fw@...len.de, netdev@...r.kernel.org,
	pablo@...filter.org, tgraf@...g.ch, amwang@...hat.com,
	kaber@...sh.net, paulmck@...ux.vnet.ibm.com,
	herbert@...dor.hengli.com.au
Subject: Re: [net-next PATCH V2 3/9] net: frag, move LRU list maintenance
 outside of rwlock

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 29 Nov 2012 09:54:19 -0800

> One element can hold about 100KB.
> 
> I guess some systems could have some worries if we consume 1024 * 5 *
> 100 KB

That's true.

Replace 1024 in your formula with X and the limit is therefore
controlled by X.

So it seems the high_thresh can be replaced with an appropriate
determination of X to size the hash.

If X is 256, that limits us to ~130MB per cpu.

We could also tweak the chain limit, call it Y, as well.
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