Date: Fri, 26 Oct 2007 15:57:14 -0500
From: Matt Mackall <mpm@selenic.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Rusty Russell <rusty@rustcorp.com.au>, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       Matthew Wilcox <willy@linux.intel.com>
Subject: Re: [PATCH 1/4] stringbuf: A string buffer implementation
Message-ID: <20071026205714.GQ17536@waste.org>
References: <20071024195847.GE27248@parisc-linux.org> <1193255992-14385-1-git-send-email-matthew@wil.cx> <200710261211.01423.rusty@rustcorp.com.au> <20071026115727.GR27248@parisc-linux.org>
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On Fri, Oct 26, 2007 at 05:57:27AM -0600, Matthew Wilcox wrote:
> On Fri, Oct 26, 2007 at 12:11:01PM +1000, Rusty Russell wrote:
> > 	This just seems like more optimization and complexity that we need.  Interfaces
> > using vsnprintf don't seem like good candidates for optimization.
> 
> That's a fair point, but I'm optimising for fewer trips into the
> slab(/slub/slob) allocator, and thus having less of an impact on the
> rest of the system.  Given that 'an alloc on every call' was one of the
> complaints Matt had about my v1 stringbuf patch, I can't imagine he'll
> be happy about this one either.

Well I expect once you start letting people easily build strings by
concatenation, you'll very shortly afterwards have people using them
in loops. And having hidden O(n^2) behavior in there is a little sad,
even though n will tend to be small and well-bounded. If we can do
something simple to avoid it, we should.

-- 
Mathematics is the supreme nostalgia of our time.
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