linux-kernel - Re: [PATCH] idr: Document ida tree sections

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Message-ID: <20130813232211.GI28996@mtj.dyndns.org>
Date:	Tue, 13 Aug 2013 19:22:11 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Kent Overstreet <kmo@...erainc.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] idr: Document ida tree sections

Hello,

On Tue, Aug 13, 2013 at 03:59:27PM -0700, Kent Overstreet wrote:
> > Well, it's not necessarily about requiring it but more about surviving
> > it with some grace when things don't go as expected, which is an
> > important characteristic for common library stuff.
> 
> The patch I posted should solve the high order allocations stuff, and
> sparseness from cyclic allocations was already solved.

I don't know.  Yeah, using vmalloc would be able to work around the
issue for most cases, I suppose.  It's iffy to consume vmalloc space
from ida, which functionally is such a basic algorithmic construct.
It probably won't worsen things noticeably but vmalloc area can be a
very precious resource on 32bit configs.

> Whatever caching optimizations you do with a radix tree version I could
> apply to this bitmap tree version, and my bitmap tree code is simpler
> and _considerably_ faster than the existing code.

But the difference won't really matter.  Cached performance would be
the same and that's likely to cover most cases, right?  It's not like
radix tree is orders of magnitude slower.

Thanks.

-- 
tejun
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