RFR: 8234863: Increase default value of MaxInlineLevel

[Claes Redestad]

Hi,

Nils raised this issue in the bug, and while I think it's a fair point I
think it's orthogonal to whether or not we can/should tune the default
here and now. I think the data we have speaks in favor of doing this
tuning for JDK 14, and then re-evaluate with more real-world data for
JDK 15, possibly dialing back the C1 defaults.

When implementing such flags we can also evaluate if C1 should be even
more conservative than it is today. It's also worth thinking about
whether or not we should introduce different settings for C1 level 1, 2
and 3..

/Claes

On 2019-12-09 12:16, Doerr, Martin wrote:
> Hi,
> 
> I think tuning inlining makes sense for C2.
> 
> The problem I see is that C1 uses the same inlining flags.
> C1 doesn't have the concept of uncommon traps so it compiles all paths.
> That's why I think this change is only good for C2.
> 
> So I suggest separating C1 inlining flags before tuning them for C2 like in the example below (note that new flags require CSR).
> Feedback for this idea is welcome.
> 
> Best regards,
> Martin
> 
> 
> 
> diff -r 45fceff98bb5 src/hotspot/share/c1/c1_globals.hpp
> --- a/src/hotspot/share/c1/c1_globals.hpp       Mon Dec 09 10:26:41 2019 +0100
> +++ b/src/hotspot/share/c1/c1_globals.hpp       Mon Dec 09 12:08:37 2019 +0100
> @@ -174,6 +174,12 @@
>     develop_pd(bool, RoundFPResults,                                          \
>             "Indicates whether rounding is needed for floating point results")\
>                                                                               \
> +  product(intx, C1MaxInlineSize, 35,                                        \
> +          "The maximum bytecode size of a method to be inlined by C1")      \
> +  product(intx, C1MaxInlineLevel, 9,                                        \
> +          "The maximum number of nested calls that are inlined by C1")      \
> +  product(intx, C1MaxRecursiveInlineLevel, 1,                               \
> +          "maximum number of nested recursive calls that are inlined")      \
>     develop(intx, NestedInliningSizeRatio, 90,                                \
>             "Percentage of prev. allowed inline size in recursive inlining")  \
>             range(0, 100)                                                     \
> 
> 
> 
> 
>> -----Original Message-----
>> From: hotspot-compiler-dev <hotspot-compiler-dev-
>> bounces at openjdk.java.net> On Behalf Of Claes Redestad
>> Sent: Montag, 9. Dezember 2019 11:15
>> To: Vladimir Kozlov <vladimir.kozlov at oracle.com>; hotspot compiler
>> <hotspot-compiler-dev at openjdk.java.net>
>> Subject: Re: RFR: 8234863: Increase default value of MaxInlineLevel
>>
>> Thanks for the review!
>>
>> /Claes
>>
>> On 2019-12-09 01:52, Vladimir Kozlov wrote:
>>> Nice finding! Good.
>>>
>>> Thanks,
>>> Vladimir
>>>
>>> On 12/8/19 1:44 PM, Claes Redestad wrote:
>>>> Hi,
>>>>
>>>> increasing MaxInlineLevel can substantially improve performance in some
>>>> benchmarks[1], and has been reported to help applications implemented
>> in
>>>> scala in particular.
>>>>
>>>> There is always some risk of regressions when tweaking the default
>>>> inlining settings. I've done a number of experiments to ascertain that
>>>> the effect of increasing this on a wide array of benchmarks. With 15 all
>>>> benchmarks tested are show either neutral or positive results, with no
>>>> observed regression w.r.t. compilation speed or code cache usage.
>>>>
>>>> Webrev: http://cr.openjdk.java.net/~redestad/8234863/open.00/
>>>>
>>>> Thanks!
>>>>
>>>> /Claes
>>>>
>>>> [1] One http://renaissance.dev sub-benchmark improve by almost 3x
>> with
>>>> an increase from 9 to 15.