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mntnoe
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Joined: 21 Jan 2007
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PostPosted: Tue Jun 05, 2007 3:27 pm    Post subject: CFLAGS and large applications Reply with quote

I want to try out compiling firefox and openoffice with the -Os flag to decrease load time, as I have a laptop with a slow harddisk.

What is your general experience with that flag on large applications? Thinking of responsiveness and such.

What is the recommended way of setting application specific CFLAGS (like using /etc/portage/package.use for USE-flags)?

Any other way to optimize applications for slow harddisks?

Thanks in advance.
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neysx
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Joined: 27 Jan 2003
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PostPosted: Tue Jun 05, 2007 3:38 pm    Post subject: Reply with quote

I also compile those two with -Os, not because of slow disks, but because -Os gives better performance overall on my dual AMD MP system.
For firefox, you need to edit /usr/portage/eclass/mozcoreconf.eclass to allow -Os (same as for -O1).
For OO.o, you need to edit the ebuild to remove the line that filters -O? and redigest it.

Hth
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Arfrever
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PostPosted: Tue Jun 05, 2007 3:47 pm    Post subject: Reply with quote

mntnoe wrote:
What is the recommended way of setting application specific CFLAGS (like using /etc/portage/package.use for USE-flags)?

Read:
Code:
man portage


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Arfrever
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Ishiki
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Joined: 31 Aug 2005
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PostPosted: Tue Jun 05, 2007 6:04 pm    Post subject: Reply with quote

mntnoe, Can you write down your start times for Firefox and OOo before and after changing -O2 to -Os ?
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mntnoe
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Joined: 21 Jan 2007
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PostPosted: Wed Jun 06, 2007 12:36 pm    Post subject: Reply with quote

I didn't notice any difference with firefox, I'm afraid. The test, however, is not that accurate:

-O2: I copied a mozilla-firefox-2.0.0.3 with pango and gnome support from my desktop top my laptop, which resulted in about 8.6 sec for a cold cache, and 2.4 sec for a warm cache.

-Os: mozilla-firefox-2.0.0.4 without pango and gnome support, compiled from scratch on my laptop. 8.3 sec/cold cache, and 2.3 sec/warm cache.

The other CFLAGS on the machines are identical. Also I used GNU time to measure the load time, and hurried to close firefox as soon as possible. So don't take the results too seriously.

From another thread I started:
eccerr0r wrote:
On my machines that I care about disk space a lot I do use -Os (specifically, CF disks). However I've found in practice it doesn't really help too much loading, burst speed reads are only a fraction of total time to satisfy requests (hint: seek times)

So I'm afraid -Os was not what I needed here.

Arfrever, I can't find it in the portage man-file. Could you please specify it?

BTW Prelinking wouldn't be a good idea when using a slow harddisk, would it?
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Arfrever
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PostPosted: Thu Jun 07, 2007 6:01 pm    Post subject: Reply with quote

mntnoe wrote:
Arfrever, I can't find it in the portage man-file. Could you please specify it?

"/etc/portage/bashrc" or "profile.bashrc" from some profile.

You can use "profile.bashrc" from "${PORTDIR}/profiles/base".
${PORTDIR}/profiles/base/profile.bashrc:
for conf in ${PN} ${PN}-${PV} ${PN}-${PV}-${PR}; do
   [[ -r ${PORTAGE_CONFIGROOT}/etc/portage/env/${CATEGORY}/${conf} ]] \
      && . ${PORTAGE_CONFIGROOT}/etc/portage/env/${CATEGORY}/${conf}
done

Example of use:
Code:
mkdir -p /etc/portage/env/sys-libs
echo -e 'CFLAGS="${CFLAGS// -ftree-vectorize/}"\nCXXFLAGS="${CXXFLAGS// -ftree-vectorize/}"' > /etc/portage/env/sys-libs/zlib



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Arfrever
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mntnoe
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PostPosted: Fri Jun 08, 2007 7:43 am    Post subject: Reply with quote

Thank you very much, that was exactly what I needed...
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