V8 3.6.6.25 with max-old-space-size greater than 1900MB?

[Joran Dirk Greef]

Recent GC changes in V8 are wreaking havoc with a production app. GC traces are showing pauses of over 22 seconds. Recent GC changes are unable to handle millions of long-lived entities.

V8 3.6.6.25 GC works perfectly.

The one problem now is getting V8 3.6.6.25 to allow max-old-space-size greater than 1900 MB on Ubuntu.

Is there any way to run V8 3.6.6.25 with max-old-space-size greater than 1900 MB?

Or is there a slightly newer version than 3.6.6.25 which allows bigger heaps but without all the new GC work?

Your help would be much appreciated.

[Yang Guo]

Could you file an issue to http://code.google.com/p/v8/issues/entry with a test case to reproduce your observation? Thanks.

Yang

[Vyacheslav Egorov]

> Recent GC changes are unable to handle millions of long-lived entities. V8 3.6.6.25 GC works perfectly.

Contrary to what you might think worst pause time for V8 3.6.x and V8
3.7 - 3.15 should be roughly the same. V8 3.7 will also do 7 GCs in a
row as a last resort.

However in 3.6 if you hit a full collection it will always pause your
app for much longer then a incremental collector of 3.7 and later
would (given that everything is tweaked correctly).

--
Vyacheslav Egorov

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[Joran Dirk Greef]

In practice it's working perfectly now. I rolled Node from v0.8 back to v0.6 and the false positive allocation errors are no longer happening. There's no more "last resort gc". Load has dropped from 100% to 1%. The gc trace looks normal now. I assumed the GC errors were due to the different version of V8 bundled with Node. Perhaps it's something in Node triggering full GC repetitively? Would Node trigger GC by itself?

[Vyacheslav Egorov]

Node should not be able to trigger last resort gc.

It can be that recent changes in V8 changed allocation patterns for
some large object (array, properties backing store etc) and this now
causes last resort GC to happen.

Unfortunately it is impossible to figure out what is going on unless
you can somehow get a back trace from inside
CollectAllAvailableGarbage.

--
Vyacheslav Egorov

[Joran Greef]

How can I get such a back trace?

On 05 Nov 2012, at 6:14 PM, v8-u...@googlegroups.com wrote:

> Node should not be able to trigger last resort gc.
>
> It can be that recent changes in V8 changed allocation patterns for
> some large object (array, properties backing store etc) and this now
> causes last resort GC to happen.
>
> Unfortunately it is impossible to figure out what is going on unless
> you can somehow get a back trace from inside
> CollectAllAvailableGarbage.
>
> --
> Vyacheslav Egorov
>
>
> On Mon, Nov 5, 2012 at 7:08 AM, Joran Dirk Greef <jo...@ronomon.com> wrote:
>> In practice it's working perfectly now. I rolled Node from v0.8 back to v0.6
>> and the false positive allocation errors are no longer happening. There's no
>> more "last resort gc". Load has dropped from 100% to 1%. The gc trace looks
>> normal now. I assumed the GC errors were due to the different version of V8
>> bundled with Node. Perhaps it's something in Node triggering full GC
>> repetitively? Would Node trigger GC by itself?
>>
>>
>> On Monday, November 5, 2012 4:53:59 PM UTC+2, Vyacheslav Egorov wrote:
>>>

>>>> Recent GC changes are unable to handle millions of long-lived entities..

[Vyacheslav Egorov]

Depends on the operating system you are running in.

Check out man backtrace if you are on Mac/Linux/BSD like OS.
Vyacheslav Egorov