RFR(xxs): 8251257: NMT: jcmd VM.native_memory scale=1 crashes target VM

[Thomas Stüfe]

Thank you David.

On Sun, Aug 9, 2020 at 8:45 AM David Holmes <david.holmes at oracle.com> wrote:

> Hi Thomas,
>
> Yes all reviewed.
>
> No need for any follow ups.
>
> Thanks,
> David
>
> On 9/08/2020 4:36 pm, Thomas Stüfe wrote:
> >
> >
> > On Sun, Aug 9, 2020 at 8:29 AM David Holmes <david.holmes at oracle.com
> > <mailto:david.holmes at oracle.com>> wrote:
> >
> >     On 9/08/2020 1:01 am, Thomas Stüfe wrote:
> >      > Hi David,
> >      >
> >      > On Sat, Aug 8, 2020 at 2:32 PM David Holmes
> >     <david.holmes at oracle.com <mailto:david.holmes at oracle.com>
> >      > <mailto:david.holmes at oracle.com
> >     <mailto:david.holmes at oracle.com>>> wrote:
> >      >
> >      >     Hi Thomas,
> >      >
> >      >     Wouldn't a scale name of "b" be more appropriate given the
> >      >     acceptance of
> >      >     "scale=b"? It seems weird to me that scale=1 is even accepted
> >     in the
> >      >     first place.
> >      >
> >      >
> >      > I am not sure what you refer to, the added case in the switch
> >     construct?
> >
> >     Yes. I expected to see
> >
> >         37   switch(scale) {
> >         38     case B: return "B";
> >         39     case K: return "KB";
> >         40     case M: return "MB";
> >         41     case G: return "GB";
> >         42   }
> >
> >     ...
> >
> >      > If yes, this is the string of the unit NMT prints its numbers
> >     with. For
> >      > byte sizes, we normally omit the unit, so I do it here too.
> >
> >     ... but if the convention is to omit the unit for bytes then that is
> >     fine. The use of "1" in the switch rather than B made this look even
> >     odder to me. And I recognise that for some reason the code uses the
> >     alias "1" instead of "B" as the primary way to refer to the "byte"
> >     scale.
> >
> >
> > Just looked at the history and I added "1" and "b" myself as values in
> > 2018 when I unified scale handling between VM.metaspace and
> > VM.native_memory (JDK-8201572).
> >
> > If it bothers you we can change this but I do not see any pressing need;
> > for me "1" works, I think it makes sense.
> >
> >      > If you object against the name of the scale as used in the scale
> >      > argument, that has been there before and changing it is not
> >     subject of
> >      > the patch. I just don't want the target VM to crash.
> >
> >     Sorry I didn't intend to suggest that you change it, just commenting
> >     that it seems quite odd to me and inconsistent with the other scale
> >     values.
> >
> >      >
> >      >     And can you please add some information to the bug report.
> >      >
> >      >
> >      > Done. I thought subject + assert printout would be sufficient,
> >     sorry for
> >      > the brevity.
> >
> >     Thanks.
> >
> >     David
> >
> >
> > So, reviewed from your side?
> >
> > ..Thomas
> >
> >      >     Thanks,
> >      >     David
> >      >
> >      >
> >      > Thank you, Thomas
> >      >
> >      >
> >      >     On 8/08/2020 4:15 pm, Thomas Stüfe wrote:
> >      >      > Hi,
> >      >      >
> >      >      > may I have a second Review please?
> >      >      >
> >      >      > All tests at SAP went through successfully, as did the
> >     jdk-submit
> >      >     tests at
> >      >      > Oracle.
> >      >      >
> >      >      > Thanks!
> >      >      >
> >      >      > ..Thomas
> >      >      >
> >      >      > On Thu, Aug 6, 2020 at 5:07 PM Thomas Stüfe
> >      >     <thomas.stuefe at gmail.com <mailto:thomas.stuefe at gmail.com>
> >     <mailto:thomas.stuefe at gmail.com <mailto:thomas.stuefe at gmail.com>>>
> >     wrote:
> >      >      >
> >      >      >> Hi,
> >      >      >>
> >      >      >> very simple small fix.
> >      >      >>
> >      >      >> jcmd VM.native_memory allows for scale=1 to print exact
> byte
> >      >     values, but
> >      >      >> crashes when printing.
> >      >      >>
> >      >      >> JBS: https://bugs.openjdk.java.net/browse/JDK-8251257
> >      >      >> webrev:
> >      >      >>
> >      >
> >
> http://cr.openjdk.java.net/~stuefe/webrevs/8251257-nmt-scale-1-crash/webrev.00/webrev/
> >      >      >>
> >      >      >> Thanks, Thomas
> >      >      >>
> >      >
> >
>