Re: 13GB dcache+inode cache hash tables

From: Daniel J Blueman
Date: Thu Jun 27 2013 - 05:08:47 EST


On 25/06/2013 17:48, Eric Dumazet wrote:
On Tue, 2013-06-25 at 16:56 +0800, Daniel J Blueman wrote:
As memory capacity increases, we see the dentry and inode cache hash
tables grow to wild sizes [1], eg 13GB is consumed on a 4.5TB system.

Perhaps a better approach adds a linear component to an exponent to give
tuned scaling, given that spatial locality is an advantage in hash table
and careful use of resources.

The same approach would fit to other hash tables (mount-cache, TCP
established, TCP bind, UDP, UDP-Lite, Dquot-cache) with different
coefficients, so perhaps we could generalise.


TCP hash table is limited to 512K slots, unless overridden.
TCP bind limited to 64K slots.
UDP limited to 64K slots.

If so what are reasonable reference points and assumptions?

I do not know what you have in mind, please show us a patch ;)
[...]

Alright, I'll see what I can get together in the next week or so when I can fit it in.

Dan
--
Daniel J Blueman
Principal Software Engineer, Numascale Asia
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