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From: David Miller <davem@davemloft.net>
Subject: Re: [net-next PATCH V2 3/9] net: frag, move LRU list maintenance
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Date: Thu, 29 Nov 2012 13:05:06 -0500 (EST)
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From: Eric Dumazet <eric.dumazet@gmail.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.