On Thu, 24 Oct 2024 09:54:05 GMT, Martin Doerr wrote:
> As I understand the comment, it says alignment <= cache line size. But the
> implementation makes alignment >= cache line size. "hyper alignment" means
> alignment > cache line size?
Correct. since encoding range must cover the full klass
On Thu, 24 Oct 2024 09:28:13 GMT, Amit Kumar wrote:
>>> But then, what exactly is the error? If it's just the test assuming that
>>> cache line size is log 6, then the test should be fixed for ppc, not
>>> hotspot.
>>
>> that is the problem, test assumes log2 of 6 for chacheline size
>
> PPC l
On Thu, 24 Oct 2024 09:22:34 GMT, Thomas Stuefe wrote:
>>> This code causes test errors in
>>> `CompressedClassPointersEncodingScheme.java` on s390 and PPC64. It forces
>>> the shift to `log_cacheline` which is 7 on PPC64 and 9 on s390. The test
>>> passes when we remove "s > log_cacheline &&
On Thu, 24 Oct 2024 09:12:34 GMT, Thomas Stuefe wrote:
> But then, what exactly is the error? If it's just the test assuming that
> cache line size is log 6, then the test should be fixed for ppc, not hotspot.
that is the problem, test assumes log2 of 6 for chacheline size
-
PR Re
On Wed, 23 Oct 2024 18:14:50 GMT, Martin Doerr wrote:
> This code causes test errors in `CompressedClassPointersEncodingScheme.java`
> on s390 and PPC64. It forces the shift to `log_cacheline` which is 7 on PPC64
> and 9 on s390. The test passes when we remove "s > log_cacheline && " from
> th
On Tue, 22 Oct 2024 13:53:03 GMT, Thomas Stuefe wrote:
>> I will do some benchmarks
>
> I did SpecJBB runs with shift of 6, 8 and 10, respectively, which amounts to
> Klass alignment of 64, 256 and 1K. Benchmark scores did not show a
> significant pattern. I did not measure CPU stats though.
>
On Thu, 19 Sep 2024 13:34:47 GMT, Thomas Stuefe wrote:
>> Do you seen any effects of this in anything other than special-crafted micro
>> benchmarks? I wonder if it would be good enough to hard-code this to be 10
>> for the first integration of Lilliput.
>
> I will do some benchmarks
I did Spe
On Tue, 8 Oct 2024 10:20:45 GMT, Albert Mingkun Yang wrote:
>> I was thinking that we should remove the entire:
>>
>> // Note: If min-fill-size decreases to 1, this whole method becomes
>> redundant.
>> assert(CollectedHeap::min_fill_size() >= 2, "inv");
>>
>> block, since it is now incorr
On Tue, 8 Oct 2024 08:12:31 GMT, Stefan Karlsson wrote:
>> I took UCOH into account when this code was written -- the current version
>> of PR would fail the following assert.
>>
>>
>> // Note: If min-fill-size decreases to 1, this whole method becomes
>> redundant.
>> assert(CollectedHe
On Tue, 8 Oct 2024 07:40:24 GMT, Albert Mingkun Yang wrote:
>> After re-reading this again I agree with what you're writing. If you make
>> the change to use:
>>
>> if (MinObjAlignment >= CollectedHeap::min_fill_size()) {
>> return;
>> }
>>
>>
>> do you even have to check for UCOH in this f
On Mon, 7 Oct 2024 11:49:21 GMT, Stefan Karlsson wrote:
>> When MinObjectAlignment=16, then that method does nothing anyway:
>>
>>
>> if (MinObjAlignment > 1) {
>> return;
>> }
>>
>>
>>
>> I think what it really means to say is
>>
>> if (MinObjAlignment >= CollectedHeap::min_fill
On Mon, 7 Oct 2024 10:49:39 GMT, Roman Kennke wrote:
>> Did you figure out if the code above is correct w.r.t.
>> `MinObjectAlignment=16`?
>
> When MinObjectAlignment=16, then that method does nothing anyway:
>
>
> if (MinObjAlignment > 1) {
> return;
> }
>
>
>
> I think what it rea
On Mon, 7 Oct 2024 08:49:58 GMT, Stefan Karlsson wrote:
>> Style note: The added code is inserted between a comment and the code that
>> the comment refers to. It would be nice to tidy this up.
>
> Did you figure out if the code above is correct w.r.t.
> `MinObjectAlignment=16`?
When MinObject
On Thu, 19 Sep 2024 05:36:41 GMT, Stefan Karlsson wrote:
>> src/hotspot/share/gc/parallel/psParallelCompact.cpp line 787:
>>
>>> 785: // The gap is always equal to min-fill-size, so nothing to do.
>>> 786: return;
>>> 787: }
>>
>> Reading the comment, it is not obvious that this is co
On Thu, 19 Sep 2024 13:08:43 GMT, Stefan Karlsson wrote:
>> Yes, please, not having this code would be really nice. This is difficult
>> code.
>
> Do you seen any effects of this in anything other than special-crafted micro
> benchmarks? I wonder if it would be good enough to hard-code this to
On Thu, 19 Sep 2024 12:35:30 GMT, Coleen Phillimore wrote:
>> Note that if we go with my KLUT proposal for post-Lilliput (the GC oop
>> iteration improvements), this will not matter anymore and can be simplified
>> to a fixed shift of 10.
>
> Yes, please, not having this code would be really ni
On Thu, 19 Sep 2024 11:47:21 GMT, Thomas Stuefe wrote:
>> It lessens the cache effects of Klass hyperaligning.
>
> Note that if we go with my KLUT proposal for post-Lilliput (the GC oop
> iteration improvements), this will not matter anymore and can be simplified
> to a fixed shift of 10.
Yes,
On Wed, 18 Sep 2024 23:53:28 GMT, Coleen Phillimore wrote:
>> Roman Kennke has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> JVMCI support
>
> src/hotspot/share/oops/compressedKlass.hpp line 175:
>
>> 173: // 5b) if CDS=off: Calls ini
On Thu, 19 Sep 2024 11:43:12 GMT, Thomas Stuefe wrote:
>> src/hotspot/share/oops/compressedKlass.cpp line 231:
>>
>>> 229: // The reason is that we want to avoid, if possible, shifts larger
>>> than
>>> 230: // a cacheline size.
>>> 231: _base = addr;
>>
>> Why is this important?
>
On Thu, 19 Sep 2024 05:44:42 GMT, Stefan Karlsson wrote:
>> Roman Kennke has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> JVMCI support
>
> src/hotspot/share/oops/compressedKlass.cpp line 231:
>
>> 229: // The reason is that we want
On Thu, 19 Sep 2024 10:29:11 GMT, Hamlin Li wrote:
>> Roman Kennke has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> JVMCI support
>
> src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp line 2529:
>
>> 2527: }
>> 2528: __ decode_
On Wed, 18 Sep 2024 23:49:34 GMT, Coleen Phillimore wrote:
>> Roman Kennke has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> JVMCI support
>
> src/hotspot/share/oops/compressedKlass.cpp line 242:
>
>> 240: } else {
>> 241:
>> 242:
On Wed, 18 Sep 2024 13:23:44 GMT, Roman Kennke wrote:
>> This is the main body of the JEP 450: Compact Object Headers (Experimental).
>>
>> It is also a follow-up to #20640, which now also includes (and supersedes)
>> #20603 and #20605, plus the Tiny Class-Pointers parts that have been
>> prev
On Thu, 19 Sep 2024 05:35:34 GMT, Stefan Karlsson wrote:
>> Roman Kennke has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> JVMCI support
>
> src/hotspot/share/gc/parallel/psParallelCompact.cpp line 787:
>
>> 785: // The gap is always
On Wed, 18 Sep 2024 13:23:44 GMT, Roman Kennke wrote:
>> This is the main body of the JEP 450: Compact Object Headers (Experimental).
>>
>> It is also a follow-up to #20640, which now also includes (and supersedes)
>> #20603 and #20605, plus the Tiny Class-Pointers parts that have been
>> prev
On Wed, 18 Sep 2024 13:23:44 GMT, Roman Kennke wrote:
>> This is the main body of the JEP 450: Compact Object Headers (Experimental).
>>
>> It is also a follow-up to #20640, which now also includes (and supersedes)
>> #20603 and #20605, plus the Tiny Class-Pointers parts that have been
>> prev
> This is the main body of the JEP 450: Compact Object Headers (Experimental).
>
> It is also a follow-up to #20640, which now also includes (and supersedes)
> #20603 and #20605, plus the Tiny Class-Pointers parts that have been
> previously missing.
>
> Main changes:
> - Introduction of the (
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