linux-kernel - Re: [PATCH 1/4] stringbuf: A string buffer implementation

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Message-ID: <20071023221116.GL17536@waste.org>
Date:	Tue, 23 Oct 2007 17:11:16 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Matthew Wilcox <matthew@....cx>
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	Matthew Wilcox <willy@...ux.intel.com>
Subject: Re: [PATCH 1/4] stringbuf: A string buffer implementation

On Tue, Oct 23, 2007 at 05:12:43PM -0400, Matthew Wilcox wrote:
> Consecutive calls to printk are non-atomic, which leads to various
> implementations for accumulating strings which can be printed in one call.
> This is a generic string buffer which can also be used for non-printk
> purposes.  There is no sb_scanf implementation yet as I haven't identified
> a user for it.

You might want to consider growing the buffer by no less than a small
constant factor like 1.3x. This will keep things that do short concats
in a loop from degrading to O(n^2) performance due to realloc and
memcpy.

> + * No locking is performed, although memory allocation is done with
> + * GFP_ATOMIC to allow it to be called when you're holding a lock.

Should probably just bite the bullet and pass a flag.

> +#define INITIAL_SIZE 32

Too small. That will guarantee that most users end up doing a realloc.
Can we have 128 instead?

-- 
Mathematics is the supreme nostalgia of our time.
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