linux-kernel - Re: [RFC 1/4] hashtable: introduce a small and naive hashtable

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Message-ID: <1343929717.9299.358.camel@edumazet-glaptop>
Date:	Thu, 02 Aug 2012 19:48:37 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Josh Triplett <josh@...htriplett.org>,
	Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	paul.gortmaker@...driver.com
Subject: Re: [RFC 1/4] hashtable: introduce a small and naive hashtable

On Thu, 2012-08-02 at 10:32 -0700, Linus Torvalds wrote:
> On Thu, Aug 2, 2012 at 9:40 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> >
> > For a trivial hash table I don't know if the abstraction is worth it.
> > For a hash table that starts off small and grows as big as you need it
> > the incent to use a hash table abstraction seems a lot stronger.
> 
> I'm not sure growing hash tables are worth it.
> 
> In the dcache layer, we have an allocated-at-boot-time sizing thing,
> and I have been playing around with a patch that makes the hash table
> statically sized (and pretty small). And it actually speeds things up!

By the way, anybody tried to tweak vmalloc() (or
alloc_large_system_hash()) to use HugePages for those large hash
tables ?



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