RFR: 8303040: linux PPC64le: Implementation of Foreign Function & Memory API (Preview) [v3]

[Martin Doerr]

On Fri, 24 Feb 2023 07:39:15 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

> > ~I don't think we've done that much testing with UseSystemMemoryBarrier since it was added~. I'm a bit nervous about turning it on by default since it's currently also used for JNI. Let's see what Robbin thinks.
> 
> For reliability: On every Oracle tier 5 we run these test two groups: vmTestbase_nsk_jvmti, open/test/hotspot/jtreg/:hotspot_runtime For each of linux_x64_debug, windows_x64, linux_aarch64_debug with sysmembar on. I picked jvmti as this is very heavy on 'JNI'. No issues reported that I know about. We also have this test: SystemMembarHandshakeTransitionTest.java which only JNI transisition with this options.
> 
> For performance, the heavy lifting is on reader of thread state and the only case I have identified is JFR.
> 
> I suggest changing the default now, if there is issues we have time to revert it back before RDP1.

Thanks for your prompt reply! I agree, this is a good time to enable it. Do you want to do it? We'll support it and run tests on our machines and platforms. I think JFR users who want a very high sampling rate can switch it off. Making the flag diagnostic is fine with me, but that shouldn't get discussed in this PR :-)

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PR: https://git.openjdk.org/jdk/pull/12708