[Vm-dev] Maximum value of -stackpages VM parameter?

Phil B pbpublist at gmail.com
Mon Jun 12 21:25:34 UTC 2017


Thanks for the info, that's good to know.  I probably should have been
explicit in that I am only bumping it up this high to troubleshoot a rather
annoying startup bug in my code. When it crashes as a result of the stack
overflow the trace is pretty useless (iirc, about 1/2 a page of INVALID
REFERENCE so I'm mostly flying blind.)  Bumping up the limit is allowing me
to get a better view of where things are going wrong and I plan to drop
back once I've resolved it.


On Jun 12, 2017 4:43 PM, "Eliot Miranda" <eliot.miranda at gmail.com> wrote:

Hi Phil,

> On Jun 12, 2017, at 12:50 PM, Phil B <pbpublist at gmail.com> wrote:
> In trying to troubleshoot an issue, I needed to bump up the stackpages
parameter.  On 64-bit Linux, a value of 600 worked but 1000 segfaulted so I
was just wondering what the limit(s) are for it?

There are no explicit limits.  The set fault you're seeing is as a result
of the stack pages being allocated on the c stack.  When the number is high
the stack overflows and boom.

A word to the wise: too high a value and scavenging performance falls
(stack pages are implicitly roots into new space), and become performance
falls (all activations in stack space are scanned post become to avoid a
read barrier on inst var fetch).

The default value was 192, a value chosen to exceed qwaq server process
usage, but both at Cadence and in Spur profiling we found that was not a
good value and pulled it back to 64 (IIRC).

I'm curious as to why are you exploring such high values.
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