From: Eric Dumazet <redacted>
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.