QtMoko Virtual Memory
David Garabana Barro
david at garabana.com
Wed Sep 1 12:38:15 CEST 2010
On Miércoles, 1 de Septiembre de 2010 11:22:45 Gennady Kupava escribió:
> В Срд, 01/09/2010 в 10:50 +0200, Nashvin Gangaram пишет:
> > * Does swap cause a significant performance increase with
> > QtMoko?
> No, i think it may cause significant performance decrease instead. But
> this just educated guess and it would be better to do some testing to
> prove this.
It's not true for me, and it's a common misunderstanding IMHO.
For testing, simply try to download tiles at zoom level 11, for the upper 6
zoom levels in tangoGPS. Better if you make it twice (moving on the map)
Without swap, it will catch all available memory, and FR will get really
slooooow, to the limit of appearing to hang, and even sometimes oomkill will
start killing some random process.
With swap, linux can swap unused pages (other daemon pages, not tangogps ones)
and tangogps will continue running, and FR will be responsible. You only will
notice some 1-4 seconds slowdown from time to time, when pages are swapped out
swap is not only for "creating" more memory. If FR starts to massively trashing
pages to swap, it will really SLOW things a lot, for sure (the same is true for
But it will help *a lot* to have more memory available for running apps.
Think on swap as a place where put unused memory pages, and use real RAM for
currently used apps or caching files from slow uSD
Swap will *ALLWAYS* help, but will help a lot more on a limited memory device,
Here  you can read more about what I'm saying.
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