On 6/20/2010 3:11 PM, Stéphane Rollandin wrote:
> A naive question: are there now specific coding guidelines for getting
> the best out of the JIT, or can we go and code as usual and expect all
> methods to run much faster automatically ?

The latter. You should expect a 2-3x performance improvement in pretty 
much any kind of code (more towards 2x when running primitive and I/O 
bound stuff; more torwards 3x when running "pure" Smalltalk code).

Examples of non-I/O bound stuff:

[Smalltalk browseAllCallsOn: #do:] timeToRun.

    Squeak: 779
    CogVM:  258

[Morph methodsDo:[:meth| meth decompileString]] timeToRun.

    Squeak: 537
    CogVM:  166

Examples of I/O heavy stuff:

[Morph compileAll] timeToRun.

    Squeak: 1510
    CogVM:   766

[saveMorphs := World submorphs.
World removeAllMorphs."heh, heh"
time := [1 to: 10 do: [:i |
	Browser fullOnClass: SystemDictionary selector: #macroBenchmarks].
	World submorphs do: [:m | m delete. self currentWorld doOneCycle].
] timeToRun ] ensure:[World addAllMorphs: saveMorphs].

     Squeak:  2633
     CogVM:   1445

As usual for benchmarks YMMV slightly depending on what you're doing but 
I'd be surprised if you wouldn't get a 2-3x performance boost regardless 
of what you're doing.

Cheers,
   - Andreas