RFR: 8233494: Avoid calling MallocTracker::record_malloc and record_free when NMT is off

[Zhengyu Gu]

Looks good to me too.

Thanks,

-Zhengyu

On 11/4/19 9:14 AM, Doerr, Martin wrote:
> Hi Claes,
> 
> this makes sense. Change looks good to me.
> 
> Best regards,
> Martin
> 
> 
>> -----Original Message-----
>> From: hotspot-runtime-dev <hotspot-runtime-dev-
>> bounces at openjdk.java.net> On Behalf Of Claes Redestad
>> Sent: Montag, 4. November 2019 14:54
>> To: Hotspot dev runtime <hotspot-runtime-dev at openjdk.java.net>
>> Subject: RFR: 8233494: Avoid calling MallocTracker::record_malloc and
>> record_free when NMT is off
>>
>> Hi,
>>
>> this patch removes some small but measurable NMT-related overheads
>> when
>> when NMT is disabled, by moving NMT_off checks out into MemTracker
>> where
>> they can be more aggressively inlined.
>>
>> Bug:    https://bugs.openjdk.java.net/browse/JDK-8233494
>> Webrev: http://cr.openjdk.java.net/~redestad/8233494/open.00/
>>
>> Motivation:
>>
>> Overhead of calling MallocTracker methods account for ~15-25% of
>> instructions retired by os::malloc/realloc/free. On a "Hello World" on
>> my laptop (no large pages) we already do roughly 9k os::malloc calls, so
>> this improvement means a reduction in instructions retired by ~250k, or
>> ~0.2% of the total. There is no discernible difference in behavior or
>> overhead for the case when NMT is enabled.
>>
>> Testing: tier1-2
>>
>> Thanks!
>>
>> /Claes