linux-kernel - Re: [v4 1/1] mm: Adaptive hash table scaling

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Message-ID: <87h90faroe.fsf@firstfloor.org>
Date:   Sat, 20 May 2017 19:07:29 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, mhocko@...nel.org
Subject: Re: [v4 1/1] mm: Adaptive hash table scaling

Pavel Tatashin <pasha.tatashin@...cle.com> writes:

> Allow hash tables to scale with memory but at slower pace, when HASH_ADAPT
> is provided every time memory quadruples the sizes of hash tables will only
> double instead of quadrupling as well. This algorithm starts working only
> when memory size reaches a certain point, currently set to 64G.
>
> This is example of dentry hash table size, before and after four various
> memory configurations:

IMHO the scale is still too aggressive. I find it very unlikely
that a 1TB machine really needs 256MB of hash table because
number of used files are unlikely to directly scale with memory.

Perhaps should just cap it at some large size, e.g. 32M

-Andi