ubuntu-phone team mailing list archive

[Tyler Hicks <tyhicks@xxxxxxxxxxxxx>]

On 2015-07-29 11:28:57, Jamie Strandboge wrote:
> On 07/29/2015 11:09 AM, Tyler Hicks wrote:
> > On 2015-07-29 11:25:27, Alberto Mardegan wrote:
> >> On 07/29/2015 07:07 AM, Tyler Hicks wrote:
> 
> >>> The exec() will need to occur after special process initialization
> >>> such as setting rlimits, configuring cgroups, etc., but before
> >>> attempting to preload any libraries.
> >>>
> >>> I've prototyped the difference with a simple proof-of-concept of a 
> >>> booster daemon and app program and the exec() slows down things a 
> >>> considerable amount. Any benchmarks should definitely include such
> >>> a change in order to not get any hopes up by looking at the
> >>> non-exec()ing benchmark numbers.
> >>
> >> But the exec() does not necessarily need to load the application,
> >> right? It could happen when the user has not yet chosen which
> >> application to start, and instead of executing an app, it could exec()
> >> into a loader process which does all library preloading and
> >> initializing, and then (when the user launches an app) dlopen the app,
> >> close any unneeded file descriptors, call aa_change_profile and
> >> finally run main(). Then of course it would have to quit, and not be
> >> reused.
> > 
> > Yes, exactly!
> > 
> >> This would still preserve the ASLR, wouldn't it?
> > 
> > Yes. I think there will still be plenty of speed benefits. I don't think
> > the memory footprint benefits of the booster processes will be nearly as
> > good, though. My whole point is that it is worth benchmarking because I
> > think we'll still good performance.
> > 
> I think it is important to note (and please correct me if I am wrong! :) that,
> today, there is no memory footprint benefit to lose because, today, we have a
> full fork/exec of each app. Therefore if we can realize 'plenty of speed
> benefits' as Tyler believes we can (and that people should benchmark), that is a
> complete 'win' for the platform.

Ah, yes, that's a great point. Thanks for mentioning that.

Tyler

> 
> -- 
> Jamie Strandboge                 http://www.ubuntu.com/
> 



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