linux-kernel - Re: [PATCHSET] idr: implement idr_alloc() and convert existing users

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Message-ID: <20130326163635.GC3061@htj.dyndns.org>
Date:	Tue, 26 Mar 2013 09:36:35 -0700
From:	Tejun Heo <tj@...nel.org>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Jeff Layton <jlayton@...hat.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, rusty@...tcorp.com.au,
	skinsbursky@...allels.com, ebiederm@...ssion.com,
	jmorris@...ei.org, axboe@...nel.dk
Subject: Re: [PATCHSET] idr: implement idr_alloc() and convert existing users

On Tue, Mar 26, 2013 at 09:33:51AM -0700, Tejun Heo wrote:
> not be too bad.  The optimal would be bitmap + hashtable, I suppose.

Oops, with more restricted (or at least dynamically adjusted) ID
space, that is.

The problem with idr is that it can get pretty wasteful if the IDs
become very scattered - the worst case being one ID per each idr_layer
(the internal allocation block).  That said, even cyclic allocation
should yield somewhat clustered IDs, so I don't think it'd be too bad.

Thanks.

-- 
tejun
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