RFC - Improving C2 Escape Analysis

[Cesar Soares Lucas]

Hi Tobias and Ron,

Thank you for providing more details about this. Really helpful!

We decided to direct our immediate efforts to improving EA for heap objects.
AFAIU inline types will bring a lot of performance improvements but that will
require the programmer to rewrite part(s) of the application - please correct
if I'm wrong here. We are investigating how we can improve the performance of
applications that aren't updated to use inline types.

About the write-up, may I ask you what do you think is the most critical
issue raised there? Or perhaps there is something else that we missed?


Cheers,
Cesar

________________________________
From: Ron Pressler <ron.pressler at oracle.com>
Sent: October 19, 2021 6:39 AM
To: Tobias Hartmann <tobias.hartmann at oracle.com>
Cc: Cesar Soares Lucas <Divino.Cesar at microsoft.com>; John Rose <john.r.rose at oracle.com>; Mark Reinhold <mark.reinhold at oracle.com>; hotspot-dev at openjdk.java.net <hotspot-dev at openjdk.java.net>; Brian Stafford <Brian.Stafford at microsoft.com>; Martijn Verburg <Martijn.Verburg at microsoft.com>
Subject: Re: RFC - Improving C2 Escape Analysis

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> On 19 Oct 2021, at 14:17, Tobias Hartmann <tobias.hartmann at oracle.com> wrote:
>
>
> That said, support for stack/thread local allocation would be something that we could potentially
> use in Valhalla to avoid buffering on the heap. It's difficult though because in most cases we use
> buffering when storing to a non-flattened field that escapes to other threads.
>


Just a reminder, stacks can move in memory (virtual threads), so great care must be
taken with pointers pointing into the stack. As a general rule, that’s a no-no.

— Ron