RFR: Caching MethodType's descriptor string improves lambda linkage performance

John Rose john.r.rose at oracle.com
Tue Sep 17 00:41:05 UTC 2013

The algorithmic change (string cache) is acceptable, although it will tend to increase footprint somewhat.  We can tweak that later if necessary.  There are probably only a small number of such strings, so maybe a small leaky map would do the trick as well.  What you propose is fine.

But, please don't hand-inline methods (checkPtype, checkSlotCount).  That is usually the wrong answer.  If there is a JIT inlining decision that isn't going right, we need to fix that, not distort the Java code.

Also, I think you deleted a call to checkSlotCount that should still be there to detect illegal inputs.  One of the costs of hand-inlining is bitrot like that.

— John

On Sep 11, 2013, at 12:03 PM, Sergey Kuksenko <sergey.kuksenko at oracle.com> wrote:

> On 09/11/2013 09:01 PM, Aleksey Shipilev wrote:
>> On 09/11/2013 08:23 PM, Sergey Kuksenko wrote:
>>> http://cr.openjdk.java.net/~skuksenko/jsr335/8024635/webrev.00/
>> As much as I hate to see the hand code tweaking instead of relying on
>> compiler to do it's job, I understand this is about interpreter. Seems
>> good then.
>> * Formatting: "if(...)" should be "if (...")
> Will do
>> * Formatting: "//NPE" should be "// null check"
> I just preserve exiting comments.
> Decided don't modify original code which is not important to required
> functionality.
>> * Formatting: "desc =  " should be "desc = "
>> * Formatting: this one should not use braces (for consistency with other
>> usages)?
>> 364         if(nptype == null) { //NPE
>> 365             throw new NullPointerException();
>> 366         }
> Let ask code owner.
>> * Explicit null-checks: implicits via .getClass and .equals always
>> bothered me in j.l.i.*; the idea was seemingly to piggyback on the
>> compiler intrinsics. 
> anyway it is doesn't matter after C1/C2
>> Any idea what's the cost of using
>> Objects.requireNonNull there?
> If we are running under the interpreter Objects.requireNonNull costs
> enough to eliminate benefits from this fine tuning.
> -- 
> Best regards,
> Sergey Kuksenko

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