Dan Williams wrote:
On Tue, 2007-03-13 at 12:04 -0500, Vladimir Makarov wrote:
William Cohen wrote:
William Cohen wrote:
Looked at where the processor spends its time when browsing the web.
Hardware configuration:
OLPC Beta 2 machine
Linksys USB200M USB 10/100 for ethernet connection
4GB memorex Mini Travel Drive for storage of image
Software configuration:
/tmp/olpc-redhat-stream-development-build-299-20070308_1417-devel_ext3.img
kernel-2.6.21-20070309.olpc1p.dc5079fafb767e4
oprofile-0.9.2-3.fc6
Re ran the experiment on build 301 and installed the
xorg-x11-server-debuginfo-1.1.99.3-0.10.2.olpc1.i386.rpm on the olpc
machine, so I could take a look at where time is being spent in libfb.so.
I don't know what version of gcc and options were used to compile the
packages. If somebody points me where to look at this, I could be more
sure. It looks to me that the packages were compiled without usage of
tunnning gcc to geode. The div and mod insn are expensive in geode.
Usage of div or shifts are choosen in gcc expmed.c and this is directed
by costs defined by -mtune or -march.
I already did gcc tunning to geode (pipeline description, code costs,
i386 port parameter values) and submitted it to the gcc mainline. As I
know Jakub Julinek was going to backport this code to redhat gcc. So I
can guess that if the right compiler and options are used, it will make
code faster (and several % smaller because -mtune=geode generates
smaller code that any other tuning).
I seem to recall that we have a gcc available that does geode tuning.
What's missing is to change the RPM_OPT_FLAGS in the olpc-1 buildroots
and then fork & recompile packages from package-cvs that we want to
optimize with geode. That by definition means that we try to recompile
only the smallest set of packages we can since it's a branch off of FC6.
We'll need to check up on this further. Vladimir, can you verify that
the version of gcc in FC6-updates right now does Geode optimizations for
us?
Sorry for slower response. Yes, Jakub added the patch for fedora 6
update gcc.
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