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Re: [PATCH] File readahead buffering

From: Colin D Bennett
Subject: Re: [PATCH] File readahead buffering
Date: Wed, 23 Jul 2008 07:33:32 -0700

On Wed, 23 Jul 2008 10:05:36 +0800
Bean <address@hidden> wrote:

> On Wed, Jul 23, 2008 at 3:06 AM, Colin D Bennett <address@hidden>
> wrote:
> > On Tue, 22 Jul 2008 14:48:31 -0400
> > Pavel Roskin <address@hidden> wrote:
> >
> >> On Tue, 2008-07-22 at 08:43 -0700, Colin D Bennett wrote:
> >> > This patch speeds up loading a TGA image on my test system from
> >> > 29 seconds to approximately 1 second.
> >> >
> >> > I noticed that on my 1 GHz test system running from an IDE
> >> > CompactFlash drive, loading a certain TGA image in GRUB takes
> >> > about 29 seconds.
> >>
> >> I'm sorry for straying from your point, but maybe we should drop
> >> TGA support.  It was the first image format for GRUB to support,
> >> but now PNG is supported, and it should be better in all aspects.
> >
> > I agree that TGA is not, in general, a great choice for an image
> > format (unless it is faster to load a large background image -- a
> > 1024x768 RGB PNG file may take more time to decompress than a TGA
> > image would take to load -- although perhaps an uncompressed PNG
> > file would be comparable in speed to load).  However, I have not
> > been able to load any PNG images that I have tried to use.
> > Something about the chunk type not being supported.
> >
> Hi,
> Please upload the png file that cause problem.
> Also note that png use DEFLATE compression. I write a decoder in png,
> which may be a little slow. Perhaps I can import the decoder from
> zlib, if copyright allows.

Ok, after some more testing, I have found that if I create PNG images
with ImageMagick or The GIMP, they work.  However, I have an image that
I was trying to use as a GRUB background which is from a MythTV theme
called Titivillus.  The PNG file from the MythTV theme doesn't load in
GRUB.  I get the message "error: png: block type fixed not supported".

The file is at
and ImageMagick's "identify -verbose" tells me it was created with
Adobe ImageReady.

Since the free tools that I've tried seem to work fine, this is not a
big deal to me, but perhaps before a widespread GRUB 2 release we might
want to improve the PNG reader compatibility.


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