Re: [gentoo-amd64] Re: gcc 4.1 upgrade - bad desktop interactivity anyone?

[Mark Knecht]

On 9/14/06, Duncan <1i5t5.duncan@×××.net> wrote:
> "Mark Knecht" <markknecht@×××××.com> posted
> 5bdc1c8b0609140715t2c135c9q50bf7ff8cbf1d82e@××××××××××.com, excerpted
> below, on  Thu, 14 Sep 2006 07:15:42 -0700:
>
> > I'm just curious whether anyone besides me is noticing their machine
> > feeling somewhat sluggish since doing the gcc-4.1 upgrade? Mine seems ot
> > be using a lot of memory. Alt-tabbing between windows seems slow.
> > Ethernet traffic in my browser is causing pretty noticeable
> > interruptions in things like MythTV.
>
> > The machine is still quite usable, but it doesn't feel as snappy as it
> > did last week.
> >
> > I made no changes in /etc/make.conf for the upgrade. Everything is
> > pretty basic as far as I can tell:
> >
> > CFLAGS="-march=k8 -O2 -pipe"
>
> > CXXFLAGS="${CFLAGS}"
>
> I've noticed rather the opposite, here.  gcc-4.1.1 compiled binaries are
> /dramatically/ faster and more efficient than 3.x.  However, I'm using a
> rather more elaborate CFLAGS/CXXFLAGS, and it's my conviction that gcc-4.1
> does better at optimizing exactly the way you've told it to.  That is, if
> you've given it inefficient optimizations, I'm convinced it makes a bad
> thing worse, while if you've chosen your optimizations well, it makes a
> good thing dramatically better.
>
> Here's my CFLAGS/CXXFLAGS:
>
> CFLAGS="-march=k8 -Os -pipe -frename-registers -fweb -freorder-blocks
> -freorder-blocks-and-partition -combine -funit-at-a-time -ftree-pre
> -fgcse-sm -fgcse-las -fgcse-after-reload -fmerge-all-constants"
>
> CXXFLAGS="-march=k8 -Os -pipe -frename-registers -fweb -freorder-blocks
> -funit-at-a-time -ftree-pre -fgcse-sm -fgcse-las -fgcse-after-reload
> -fmerge-all-constants"
>
<SNIP>
>
> As I said, with the above, there's a /dramatic/ improvement in
> performance between gcc-3.x and gcc-4.1.x.
>
> --
> Duncan - List replies preferred.   No HTML msgs.

Hi Duncan,
   As always, very deep thanks for the answer. Very informative and interesting.

   Now, you are very adept at this. You're explanations make sense to
the level I've considered them. (Not very far right now...) Main
questions:

1) What can be done to test this out at my end without making a 2-day
commitment to rebuild the complete machine. Is it possibly to rebuild
only portions of the machine using a different set of flags or is it a
system wide commitment requiring that I rebuild 575 packages as I did
last weekend?

2) What about building the kernel? How do the standard

make && make modules_install

command make any use of the flags in /etc/make.conf?

   This machine is a fairly standard desktop running Xorg-7, Gnome and
just a few apps most of the time. However I am an audio oriented
person so my kernel is rt-sources from the proaudio overlay. (Ingo
Molnar's patches to the kernel.org kernels and not a Gentoo kernel.) I
need to ensure that the audio stuff (Jack, Ardour, Aqualung, 1394 hard
drives) continue to work well.

   Your ideas are most welcome.

Thanks,
Mark
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