JVM inserting guard pages into stack of initial thread - will that stop with Java 10?

[Doerr, Martin]

Hi Andrew,

thanks for your reply. I guess that the performance impact will be negligible if we have enough inlining (which reduces the number of stack checks). Reducing complexity and saving stack space sounds more valuable to me.
I may consider making experiments when I find some time for it.

Best regards,
Martin


-----Original Message-----
From: Andrew Haley [mailto:aph at redhat.com] 
Sent: Dienstag, 24. Oktober 2017 11:24
To: Doerr, Martin <martin.doerr at sap.com>; Tomas Kalibera <tomas.kalibera at gmail.com>; hotspot-runtime-dev at openjdk.java.net
Subject: Re: JVM inserting guard pages into stack of initial thread - will that stop with Java 10?

On 23/10/17 18:25, Doerr, Martin wrote:

> after reading several mails about guard page problems (and quite
> some own bad experience), I wonder if they are really worth all the
> pain. Is the performance benefit from stack banging so great, that
> it justifies the tremendous complexity?
> 
> If not, I'd vote for replacing them by explicit checks. Loading a
> limit from the Thread and performing a comparison doesn't sound so
> expensive.
> 
> It could be the case that some platforms need banging (e.g. Windows
> due to on demand committed stack), but probably not all.
> Am I missing anything?

I think you should try it and tell us the results.  If we have
power-of-2 stack sizes it can be done without any loads at all, but
that's probably too restrictive, and we've had quite enough
tricksiness.  It's hard to beat the speed of a simple store, though.

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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