[External] : Re: ReplayCompiles as non-develop switch ?

[Vladimir Kozlov]

On 8/16/22 9:01 PM, Thomas Stüfe wrote:
> On Tue, Aug 16, 2022 at 9:00 PM Vladimir Kozlov <vladimir.kozlov at oracle.com <mailto:vladimir.kozlov at oracle.com>> wrote:
> 
>     On 8/16/22 10:05 AM, Thomas Stüfe wrote:
>      > Hi,
>      >
>      > Is there a particular reason why ReplayCompiles needs to be a develop switch? Or was it just not considered useful
>      > without asserts?
> 
>     It replays compilation which we want to debug in debug VM. Why do you want it be `product` flag?
> 
>     We have DumpReplayDataOnError product flag to dump compiler replay data from product VM:
>     https://github.com/openjdk/jdk/blob/master/src/hotspot/share/compiler/compiler_globals.hpp#L331
>     <https://urldefense.com/v3/__https://github.com/openjdk/jdk/blob/master/src/hotspot/share/compiler/compiler_globals.hpp*L331__;Iw!!ACWV5N9M2RV99hQ!JRgjhoZKOMvpjeekz0FN5_oc8OR6PZp-lDqLr7W_AEpu5wV0xtVtbCvvgD_XWCIeoqN88QPk0i9nNBU6w2OexzZiW4G-$>
> 
> 
> Hi Vladimir,
> 
> to reproduce a compiler error in a release VM.
> 
> - to experiment what its effect is on a VM that was actually shipped to customers, without using a debug VM and 
> switching tens of asserts off. E.g., in the case of https://bugs.openjdk.org/browse/JDK-8291665 
> <https://bugs.openjdk.org/browse/JDK-8291665>, how steep and how quickly RSS raises, and whether the raise limits itself 
> or is infinite.
> - to see whether a certain build of a shipped VM is actually affected by a certain bug. Not every bug surfaces in every 
> build.
> 
> None of that are very hard reasons, and these situations are rare. But they do occur, and it would be a bit more 
> convenient to have this switch.

So you want it for verification purpose and not for debugging an issue. We did not consider it when implemented.
I agree it could be useful and it is not hard to convert ReplayCompiles to diagnostic flag.
It will increase VM size but not much.

File RFE.

Thanks,
Vladimir K

> 
> Cheers, Thomas
> 
>