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Order file development guide

1. Build chromeos-chrome with profile instrumentation
export USE="$USE -reorder"
export EXTRA_BUILD_ARGS="order_profiling=1 order_text_section=''"

2. Add --no-sandbox to chrome start arguments (in the buttom of /sbin/session_manager_setup.sh).

3. As you prepare, you may have run chrome collecting logs (which you don't want yet). Remove them and reboot.
rm /var/log/chrome/cyglog.*; sudo reboot

4. After you browse several sites (google.com, maps.google.com, youtube.com), copy logs to your host machine to some directory.

5. Sanitize logs.
head -1 cyglog.*
If some log does not contain header (containing /opt/google/chrome/chrome), remove it. This log left from before you removed all cyglogs last boot.

6. Merge logs to a single file. This may take some minutes to run.
$CHROME_SRC/tools/cygprofile/mergetraces.py `ls cyglog.* -Sr` > merged_cyglog

7. Symbolize the log using your instrumented image (from p.1).
$CHROME_SRC/tools/cygprofile/symbolize.py -t orderfile merged_cyglog /build/x86-alex/opt/google/chrome/chrome > unpatched_orderfile

8. Rebuild chromeos-chrome with new orderfile.
export USE="$USE -reorder"
export EXTRA_BUILD_ARGS="order_profiling=0 order_text_section='/home/$USER/trunk/src/scripts/cyglog/unpatched_orderfile'"

9. Patch the orderfile to
$CHROME_SRC/tools/cygprofile/patch_orderfile.py unpatched_orderfile /build/x86-alex/opt/google/chrome/chrome > orderfile

9. If you want to visually check that the resulting image is reordered, use 
nm -Sn /build/x86-alex/opt/google/chrome/chrome | less
And note, that ChromeMain symbol is not at the beginning of symbols. 
In the image built without reordering, ChromeMain immediately follows main and is about 10th symbol in the image.

10. Update the repository containing orderfiles.
The repo, containing orderfiles is here: http://git.chromium.org/gitweb/?p=chromiumos/profile/chromium.git
Intructions on how to update the repo: http://www.chromium.org/chromium-os/how-tos-and-troubleshooting/git-server-side-information

11. Update src/third_party/chromiumos-overlay/chromeos-base/chromeos-chrome/chromeos-chrome-9999.ebuild to grab the latest version of the orderfile (that you updated in p.10).

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