On 08/16/2012 02:27 AM, Markus F.X.J. Oberhumer wrote:

On 2012-08-15 16:45, Johannes Stezenbach wrote:

quoted

On Wed, Aug 15, 2012 at 02:02:43PM +0200, Markus F.X.J. Oberhumer wrote:

quoted

On 2012-08-14 14:39, Johannes Stezenbach wrote:

quoted

On Tue, Aug 14, 2012 at 01:44:02AM +0200, Markus F.X.J. Oberhumer wrote:

quoted

On 2012-07-16 20:30, Markus F.X.J. Oberhumer wrote:

quoted

As stated in the README this version is significantly faster (typically more
than 2 times faster!) than the current version, has been thoroughly tested on
x86_64/i386/powerpc platforms and is intended to get included into the
official Linux 3.6 or 3.7 release.

I encourage all compression users to test and benchmark this new version,
and I also would ask some official LZO maintainer to convert the updated
source files into a GIT commit and possibly push it to Linus or linux-next.

Sorry for not reporting earlier, but I didn't have time to do real
benchmarks, just a quick test on ARM926EJ-S using barebox,
and found in the new version decompression is slower:
http://lists.infradead.org/pipermail/barebox/2012-July/008268.html

I can only guess, but maybe your ARM cpu does not have an efficient
implementation of {get,put}_unaligned().

Yes, ARMv5 cannot do unaligned access.  ARMv6+ could, but
I think the Linux kernel normally traps it for debug,
all ARM seem to use generic {get,put}_unaligned() implementation
which use byte access and shift.

Hmm - I could imagine that we're wasting a lot of possible speed gain
by not exploiting that feature on ARMv6+.

Or you could just realize that unaligned accesses are slow in the best 
case, and are simply not supported on some processors.

If you think a little bit, I bet you could come up with a solution that 
operates at cacheline-aligned granularity, something that would be _even 
faster_ than simply fixing the code to do aligned accesses.

	Jeff