[PATCH] 8217561 : X86: Add floating-point Math.min/max intrinsics, approval request
bsrbnd at gmail.com
Wed Feb 27 16:42:36 UTC 2019
On Tue, 26 Feb 2019 at 22:34, Vladimir Kozlov
<vladimir.kozlov at oracle.com> wrote:
> On 2/26/19 1:14 PM, B. Blaser wrote:
> > Hi Vladimir,
> > On Tue, 26 Feb 2019 at 21:50, Vladimir Kozlov
> > <vladimir.kozlov at oracle.com> wrote:
> >> Hi Bernard,
> >> Unfortunately HotSpot does not collect profiling information per call site.
> >> Currently calee's data is collected from all call sites. For example, you can have 2 calls with same *swapped* arguments
> >> and you will get your balance == 0.
> >> I would assume if you have multiply call sites in application the profiling data will be "flat" - balance value will be
> >> near 0.
> >> We did experiment few years ago to collect data per call site but we got negative result - no significant improvement in
> >> code quality in cost of a lot more memory used for MethodData.
> >> But your case (and cmove) is special since MDO is small for these methods. The only downside is to implement that you
> >> will need a lot more complex changes in HotSpot.
> >> https://bugs.openjdk.java.net/browse/JDK-8015416
> >> Note, your code is correct in a sense that it use the same profiling data as it currently used for inlining these
> >> methods. So I don't want to reject changes from the start.
> >> The only simple solution I can think of is to use intrinsic only for hottest call site. Compare invocation_count with
> >> caller's call site count to find if it is most used site which contributed the most profiling data.
> >> Thanks,
> >> Vladimir
> > Thanks for your feedback.
> > I pushed webrev.05 to jdk/submit a while ago but once I have the
> > results I'll update the patch as you suggested; the heuristic will
> > bail out if the caller didn't contribute enough to the statistics, let
> > say something like at least 80%?
> Yes, this sounds good.
Please let me know if you've any more comments or if I can push this
to the main-line (jdk/jdk) once I've got positive test results?
More information about the hotspot-compiler-dev