[Sugar-devel] Research: 0.84 Launcher Cost

[Gary Martin]

On 28 Oct 2010, at 04:34, James Cameron <quozl at laptop.org> wrote:

> Earlier in the context of SL#2080 patch review, I had said "the
> launcher is stealing CPU cycles from the startup of the activity, the
> task run queue shows this during a launch.  I wonder if activities
> might start up faster if there was no launcher, just a busy cursor."
> 
> Looks like activities would start faster; between one and four seconds,
> mostly depending on the activity, and slightly depending on the icon
> complexity.
> 
> Details below.
> 
> --
> 
> Research: will activities start faster if there is no launcher?
> 
> Method: using an XO-1, freshly installed with Sugar 0.84.22, as part
> of OLPC OS 10.1.2 build os852, test the startup time of three
> activities (Memorize, Moon and Chat), remove the launcher, retest,
> subtract.
> 
> The launcher is implemented by source file launcher.py in
> /usr/lib/python2.6/site-packages/jarabe/view/ ... the modification
> made is attached as a patch.
> 
> The times were captured with a stopwatch.  The timing began when "Start"
> was selected from the list view, and ended once the activity had
> completed display of the UI.
> 
> Result:
> 
> a.  unmodified launcher.py
> 
> Memorize-34 9.43s, 9.56s, 9.51s
> Moon-11 11.58s, 11.60s, 11.65s
> Chat-65 6.65s, 6.54s, 6.59s
> 
> b.  modified launcher.py (black background, no animation),
> 
> Memorize-34 7.60s, 7.63s, 7.60s
> Moon-11 7.78s, 7.78s, 7.95s
> Chat-65 5.04s, 4.93s, 4.88s
> 
> c.  calculated cost of launcher
> 
> Memorize-34 1.89s
> Moon-11 3.73s
> Chat-65 1.64s
> 
> Diagnosis: removing the launcher animation saved between one and four
> seconds of startup time.  The saving was greatest for the Moon activity.

Agreed, when Wade was working on this a year back or so, we came to the same estimate of about 4 sec for the launcher (should be in the mail list archives somewhere). I mentioned in a previous email that Wade managed to shave ~2 sec off this by pausing at the peek and trough of the pulse sine wave. However this did not land in time, so this is still 2sec up for grabs if some one wants to tweak and add pulse delays... You might even find Wade's patches for this ready to go if you go digging - I seem to remember the only reason it didn't land was a lack of time to test the change (was just Wade and me testing I think).

--Gary  

> --
> 
> Research: determine if the SVG icon for the Moon activity contributes
> to the delay.
> 
> Method: swap the icons, restart Sugar, retest only Chat activity with
> Moon icon.
> 
> Result:
> 
> a.  unmodified launcher.py
> 
> Chat-65 7.83s, 7.59s, 7.62s
> 
> b.  modified launcher.py (black background, no animation),
> 
> Chat-65 4.99s, 4.87s, 4.90s
> 
> c.  calculated cost of launcher
> 
> Chat-65 2.75s (greater than previous)
> 
> d.  calculated cost of moon icon over chat icon
> 
> Chat-65 1.09s
> 
> Diagnosis: the degree of saving has a little to do with the SVG icon
> complexity.  The degree of saving has much to do with the mix of
> operations performed by the activity during startup.
> 
> --
> 
> So, between 23 and 92 wasted days of looking at the launcher across
> two million laptops.  Good time to think and plan, kids.
> 
> -- 
> James Cameron
> http://quozl.linux.org.au/
> <launcher-disable.patch>
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