[cap-talk] Domain optimisation (was: Domain change (IPC?) overhead)

[Valerio Bellizzomi]

On 26/03/2008, at 21.54, John McCabe-Dansted wrote:

>On Tue, Mar 25, 2008 at 4:41 AM, Jonathan S. Shapiro <shap at eros-os.com>
>wrote:
>> On Mon, 2008-03-24 at 11:54 -0700, Jed Donnelley wrote:
>>  > On 3/24/2008 9:52 AM, Jonathan S. Shapiro wrote:
>> > > However: robustness implies introducing IPC, and each IPC adds
>overhead.
>>  > > As applications are factored and multiple layers of IPC are
>introduced,
>>  > > performance of IPC becomes critical very quickly.
>>  >
>>  > Isn't the above consideration where the language systems for
>>  > POLA provide significant additional value?
>>
>>  Not clear. Depends on what percentage of your IPCs are doing data
>>  motion. If you want to avoid storage denial of service issues and keep
>>  GC local to each domain, you still have a copy boundary at the domain
>>  boundary, and the copy cost can get large.
>
>OTOH, decomposing an application into different GC domains also has
>the potential to improve performance, by perhaps 15%, as different
>algorithms perform better under different GC mechanisms:
>  http://research.microsoft.com/~dtarditi/dist/ismm-2000a.pdf
>
>So, even from a performance point-of-view, cramming everything into
>one huge unaccountable resource pool may not be optimal.
>
>As mentioned elsewhere in the thread, from a security point-of-view it
>hardly seems necessary to put every one-line function in its own GC
>domain. Even on a typical oo-cap system I'd say that someone who could
>social engineer a malicious module into an application could typically
>do far more insidious things than crash a vat. Code that has no trust
>relationship at all (e.g. random applets off the web) could still be
>put in their own vat.
>
>-- 
>John C. McCabe-Dansted
>PhD Student
>University of Western Australia


There is a fundamental issue that makes every application unique, which
hasn't been raised yet: At which rate garbage appears ?


val