RFR(XS): 8193521: glibc wastes memory with default configuration

[Doerr, Martin]

Hi Andrew,

thanks for your feedback. I'm not really an expert on this topic and I'm hoping that people on the mailing list can help evaluating the risk and the benefit.
Own native libraries are a good point. But I still hope that there are enough people out there who would like to see improvements for their use case.

Best regards,
Martin


-----Original Message-----
From: Andrew Dinn [mailto:adinn at redhat.com] 
Sent: Donnerstag, 14. Dezember 2017 17:27
To: Doerr, Martin <martin.doerr at sap.com>; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR(XS): 8193521: glibc wastes memory with default configuration

Hi Martin,

On 14/12/17 16:00, Doerr, Martin wrote:
> I suggest to use mallopt(M_ARENA_MAX, 1). It is supported since glibc
> 2.15. I don't think that we still support older versions with
> jdk10/11.

 . . .

> I'm not aware of performance critical concurrent malloc usages in the
> JVM. Maybe somebody else is? Comments are welcome. I will also need a
> sponsor if this change is desired.

I appreciate the motivation for proposing this and I don't know of any
issues it might cause for the JVM itself. However, it might cause
problems for some of the libraries the JVM links or, indeed, for Java
apps that employ their own native libraries. The former risk could, in
theory, be assessed. The latter one is unquantifiable but needs to be
taken seriously. So, I think this change is probably not safe.

regards,


Andrew Dinn
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