RFR (S) 8235765: Use of the long type should be avoided in shared code
Coleen Phillimore
coleen.phillimore at oracle.com
Wed Aug 12 22:56:44 UTC 2020
On 8/12/20 4:43 PM, Coleen Phillimore wrote:
>
> Hi Vladimir, Thank you for looking at this change.
>
> On 8/12/20 1:25 PM, Vladimir Kozlov wrote:
>> Hi Coleen,
>>
>> I think it is safe to use 'uint' (uint32_t) for all counts in sweeper.
>>
>> What is a story about using int64_t vs jlong? And others *_t vs j*
>> types.
>
> jlong is a signed type (either long or long long) so in mutex, even
> though uint64_t makes more sense, I used int64_t so that they'd be
> convertible to jlong in the PlatformMutex layer. I didn't want to
> pull the string of this sweater even further to convert the jlong to
> uint64_t in that layer. (If that's even the right thing to do). We
> have been trying to avoid using java types like jint, jlong etc, in
> shared code, but they're pretty much everywhere.
>>
>> Also you need to look on JFR code which collect these data:
>>
>> src/hotspot//share/jfr/periodic/jfrPeriodic.cpp:
>> event.set_methodReclaimedCount(NMethodSweeper::total_nof_methods_reclaimed());
>>
>> src/hotspot//share/jfr/metadata/metadata.xml: <Field type="int"
>> name="methodReclaimedCount" label="Methods Reclaimed" />
>>
>> And I found that metadata.xml have several 'long' uses too:
>>
>> src/hotspot//share/jfr/metadata/metadata.xml: <Field type="long"
>> contentType="millis" name="peakTimeSpent" label="Peak Time" />
>>
>> Looking on codecache code and sweeper and I see a lot of
>> inconsistencies in used types :(
>> May be we need an other (compiler) RFE to clean that up.
>
> Yes, I agree. I'm going to revert sweeper, nmethod and vmStructs. It's
> better that 'long' is fixed individually in the sweeper and associated
> files.
>
> The JFR metadata.xml has a lot of "long" types declared in it. I'm
> going to revert compileBroker.* too. This is going to have to be
> fixed a little at a time.
>
> I'm testing a new more limited version of this change now.
This is a more limited attempt at stomping out 'long' in the shared code.
open webrev at http://cr.openjdk.java.net/~coleenp/2020/8235765.02/webrev
thanks,
Coleen
>
> Thanks,
> Coleen
>>
>> Regards,
>> Vladimir K
>>
>> On 8/12/20 10:00 AM, Coleen Phillimore wrote:
>>>
>>>
>>> On 8/12/20 12:19 PM, Lois Foltan wrote:
>>>> On 8/12/2020 11:21 AM, Coleen Phillimore wrote:
>>>>> Summary: Changed some long declarations to uint64_t/int64_t or
>>>>> unsigned int, depending on context.
>>>>>
>>>>> There are still 'long' declarations left in the code, but they
>>>>> should be changed by developers when working in that code and not
>>>>> as a blanket change. I didn't change a couple of longs in
>>>>> jfr/leakprofiler, for example. These are the ones I changed
>>>>> though with some explanation of why:
>>>>>
>>>>> src/hotspot/share/memory/filemap.hpp
>>>>>
>>>>> This can be negative so changed to int64_t.
>>>>>
>>>>> src/hotspot/share/runtime/mutex.cpp
>>>>>
>>>>> The PlatformMutex code takes jlong, which is signed, so that's why
>>>>> I changed these to int64_t.
>>>>>
>>>>> runtime/interfaceSupport.inline.hpp
>>>>>
>>>>> These counters are actually intervals so I changed them to
>>>>> unsigned int.
>>>>>
>>>>> src/hotspot/share/compiler/compileBroker.hpp
>>>>>
>>>>> _peak_compilation_time is signed because it is compared with jlong
>>>>> which is signed.
>>>>> Same with total_compilation_time - elapsedTimer.milliseconds()
>>>>> returns jlong.
>>>>>
>>>>> Tested with tier1-3. Tier1 on linux-x64-debug, windows-x64-debug,
>>>>> macosx-x64-debug, linux-aarch64-debug. Also built on:
>>>>> linux-arm32,linux-ppc64le-debug,linux-s390x-debug,linux-x64-zero.
>>>>>
>>>>> open webrev at
>>>>> http://cr.openjdk.java.net/~coleenp/2020/8235765.01/webrev
>>>>> bug link https://bugs.openjdk.java.net/browse/JDK-8235765
>>>>>
>>>>> Thanks,
>>>>> Coleen
>>>>
>>>> Hi Coleen,
>>>>
>>>> Looks good.
>>>>
>>>> - runtime/sweeper.hpp
>>>> This is the only file that I wondered why you changed long to
>>>> int64_t for _total_nof_methods_reclaimed and
>>>> _total_nof_c2_methods_reclaimed. Note that the method
>>>> NMethodSweeper::total_nof_methods_reclaimed returns an int. Could
>>>> both of these fields be changed to int instead?
>>>
>>> Hi Lois, Thank you for looking at this. Unfortunately, this was an
>>> outdated webrev, can you hit reload? I changed these fields to be
>>> uint64_t because they're never signed. It's likely that the number
>>> of methods is never greater than an int, but since it was long to
>>> begin with, I kept 64 bit until someone decides an 'int' is better.
>>> Since number_of_codecache_sweeps is uint64_t, which seems like a lot
>>> too, there could be that many nmethods reclaimed. I retested with
>>> windows just now to be sure.
>>>
>>> Thanks,
>>> Coleen
>>>
>>>
>>>>
>>>> Thanks,
>>>> Lois
>>>
>
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