Hi Holger,

I'm sorry for the delay since you reported the bug. Everyone working on the VM is very busy (In my case, my time is consumed by my phd and sista, I'm trying to open an alpha of the image+runtime before ESUG running at ~1.5x).

Now that the VM profiler is fully working I was able to look into the regression.

Old VM vanilla code:

27.94% (11.54%) scavengeReferentsOf (528) (27.94%)

10.21% ( 4.22%) processWeakSurvivor (193) (38.15%)

8.15% ( 3.36%) copyAndForward (154) (46.30%)

7.41% ( 3.06%) doScavenge (140) (53.70%)

5.19% ( 2.14%) lookupOrdinaryNoMNUEtcInClass (98) (58.89%)

4.71% ( 1.94%) primitiveStringReplace (89) (63.60%)

4.29% ( 1.77%) moveFramesInthroughtoPage (81) (67.88%)

2.06% ( 0.85%) isWidowedContext (39) (69.95%)

[...]

0.90% ( 0.37%) ceSendFromInLineCacheMiss (17) (85.61%)

0.85% ( 0.35%) addNewMethodToCache (16) (86.46%)

New VM vanilla code:

% of vanilla vm code (% of total) (samples) (cumulative)

22.41% (10.44%) scavengeReferentsOf (609) (22.41%)

14.46% ( 6.74%) lookupOrdinaryNoMNUEtcInClass (393) (36.87%)

6.88% ( 3.21%) copyAndForward (187) (43.75%)

6.59% ( 3.07%) processWeakSurvivor (179) (50.33%)

6.36% ( 2.97%) addNewMethodToCache (173) (56.70%)

4.19% ( 1.95%) doScavenge (114) (60.89%)

4.08% ( 1.90%) primitiveStringReplace (111) (64.97%)

2.91% ( 1.35%) moveFramesInthroughtoPage (79) (67.88%)

2.87% ( 1.34%) ceSendFromInLineCacheMiss (78) (70.75%)

2.21% ( 1.03%) marryFrameSP (60) (72.96%)

1.80% ( 0.84%) executeNewMethod (49) (74.76%)

1.36% ( 0.63%) isWidowedContext (37) (76.12%)

I highlighted the problematic methods. It is likely that it has to do with slang inlining.

The 3 methods highlighted seems to be responsible for an overhead of ~8.5% in the overall runtime. You seem to have an overhead of ~14% on my machine. There's quite a difference. The slang inlining overhead may have impacted other functions, and C profilers are never 100% accurate, so we will see when the problem is fixed if something else is also problematic. Now that we know what the problem is, I believe it will be fixed in the incoming weeks when someone (likely Eliot, maybe me) has time. Thanks for reporting the regression.

Regards

Clement