RFR (M): 8212657: Implementation of JDK-8204089 Timely Reduce Unused Committed Memory

[Ruslan Synytsky]

On Tue, 18 Dec 2018 at 12:03, Aleksey Shipilev <shade at redhat.com> wrote:

> On 12/18/18 11:39 AM, Thomas Schatzl wrote:
> >> One more minor suggestion - G1PeriodicGCInterval should be defined in
> >> milliseconds at the moment which seems impractical to me. Not clear
> >> why somebody would need to trigger GC less than in minutes, so people
> >> will always write a lot of 000. Can we update it to seconds at least?
> >
> > You can use SI prefixes like "k" or "M" (probably do not need "G" :) )
> > to reduce the number of zeros.
> >
> > Not really hung up on the scale, I am going to ask for more opinions.
> > We need to come to a conclusion relatively quickly though as we are
> > late in the release process already.
> >
> > I think the reason for choosing ms is because so far all times were in
> > ms, and Shenandoah also uses that scale. Otoh J9 uses seconds too.
>
> Shenandoah also chose "ms" for consistency reasons.
>
> In practical terms, sometimes there is a compelling need to do
> _concurrent_ GC more frequently than
> once a second. Think about tiny heap and GC taking just a few
> milliseconds. Then, to keep memory
> footprint under control, it would make sense to do GC every, say, 300
> milliseconds. This is probably
> a bad idea for the STW GC, but still can be tolerable if GC cycle is in
> milliseconds range.


> Unfortunately, we don't have support for SI prefixes going downwards from
> 1 (e.g. milli-, micro-),
> right? Keeping the units in milliseconds, and slapping the SI prefix would
> be much more confusing
> with 1K meaning "1 second"...
>

Ok, having support of prefixes is solving the issue. Just checked it for
G1PeriodicGCInterval - 1k is the same as 1K = 1 second.

Regards


>
> -Aleksey
>
>

-- 
Ruslan
CEO @ Jelastic <https://jelastic.com/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/hotspot-gc-dev/attachments/20181218/16b2893c/attachment.htm>