Re: [PATCH] File readahead buffering

[Colin D Bennett <colin@gibibit.com>]

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On Wed, 23 Jul 2008 07:33:32 -0700
Colin D Bennett <colin@gibibit.com> wrote:

> On Wed, 23 Jul 2008 10:05:36 +0800
> Bean <bean123ch@gmail.com> wrote:
> 
> > On Wed, Jul 23, 2008 at 3:06 AM, Colin D Bennett <colin@gibibit.com>
> > wrote:
> > > On Tue, 22 Jul 2008 14:48:31 -0400
> > > Pavel Roskin <proski@gnu.org> 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".

Oops!  After more testing, I have found PNG images that I saved in The
GIMP which also refuse to load due to the "block type fixed not
supported" error.  One ZIP file [1] contains images that all fail to
load in GRUB with that error, and the other [2] contains similar images
that load just fine.

[1] gibibit.com/upload/grub-png-bad.zip
[2] gibibit.com/upload/grub-png-good.zip

Regards,
Colin

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