RFR(XS): 8232533: G1 uses only a single thread for pretouching the java heap

[sangheon.kim at oracle.com]

Hi Thomas and Stefan,

On 11/19/19 1:11 AM, Stefan Johansson wrote:
>
>
> On 2019-11-19 09:35, Thomas Schatzl wrote:
>> Hi,
>>
>> On 18.11.19 22:31, sangheon.kim at oracle.com wrote:
>>> Hi all,
>>>
>>> Can I have some reviews for this small patch?
>>>
>>> G1 initiates only 1 GC thread for faster start-up and then 
>>> initialize more when we need more GC threads.
>>> This is also same when we enable +AlwaysPreTouch option, so 1 thread 
>>> touching all heap situation happens as the CR described.
>>>
>>> The proposed patch is trying to cap the total worker thread count 
>>> instead of active worker thread count. And this will make faster 
>>> start-up as well.
>>
>>    the rationale is that supposedly if a user is specifying 
>> AlwaysPreTouch, he wants best performance, and does not care so much 
>> about initializing the time it takes to initialize the extra threads. 
>> Also initializing the threads first and then doing the work in 
>> parallel should be faster than pretouching with only a single thread. :)
>>
>> I.e. in the case of the CR, it takes 2mins to pretouch the heap - 
>> initializing the threads shouldn't be that slow :P
>>
>>>
>>> CR: https://bugs.openjdk.java.net/browse/JDK-8232533
>>> Webrev: http://cr.openjdk.java.net/~sangheki/8232533/webrev.0/
>>> Testing: hs-tier1
>>
>> Please fix the copyright date before pushing if you want. I do not 
>> need a re-review for this change. Looks good otherwise.
> Looks good to me too,
> Stefan
Thanks for your review.
I will update the copyright year before pushing.

Thanks,
Sangheon


>>
>> Thanks,
>>    Thomas