[8u] RFR: 8144483: One long Safepoint pause directly after each GC log rotation

[Bertrand Delsart]

And to me too of course :-)

Bertrand.

On 1/7/16 11:41 AM, David Holmes wrote:
> Hi Cheleswer,
>
> This workaround seems fine to me.
>
> Thanks,
> David
>
> On 6/01/2016 9:37 PM, cheleswer sahu wrote:
>> Hi,
>>
>> Please review the code changes for
>> "https://bugs.openjdk.java.net/browse/JDK-8144483".
>>
>> webrev link: http://cr.openjdk.java.net/~kevinw/8144483/webrev.00/
>> JBS link: https://bugs.openjdk.java.net/browse/JDK-8144483
>>
>> Bug brief:
>> A long pause is observed after each gc log rotation in Solaris.
>>
>> Problem Identified:
>> In each GC log rotation "print_memory_info()" is getting called through
>> dump_loggc_header().
>> "print_memory_info()" of solaris version calls check_addr0(st);
>>
>> File:
>> http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/file/80959a760b85/src/os/solaris/vm/os_solaris.cpp
>>
>>
>>
>> void os::print_memory_info(outputStream* st) {
>>    st->print("Memory:");
>>
>>    st->print(" %dk page", os::vm_page_size()>>10);
>>
>>    st->print(", physical " UINT64_FORMAT "k", os::physical_memory()>>10);
>>
>>    st->print("(" UINT64_FORMAT "k free)", os::available_memory() >> 10);
>>
>>    st->cr();
>>   (void) check_addr0(st);
>> }
>>
>> Now check_addr0(st) function do a lot of read call to read the data from
>> /proc/self/map.
>> and check if virtual address is mapped to 0x0. These read calls take lot
>> of time which results in GC rotation pause.
>> Here calling check_addr0() seems unnecessary for every log rotation. It
>> will be more logical if this function gets called only
>> when an error is reported.
>>
>> Solution proposed:
>> Before GC log rotation print_memory_info() is ever getting called from
>> Vm_error.cpp during error reporting. And in case of error reporting
>> checking for address mapping to 0x0 looks fine. So the proposed solution
>> is to do an extra check inside print_memory_info().
>>
>> -  (void) check_addr0(st);
>> +  if (VMError::fatal_error_in_progress()){
>> +     (void) check_addr0(st);
>> +  }
>>   }
>>
>>   This check doesn't fit well inside printing function, but at this
>> point I don't see the need to create a new os:: method and change all
>> the OS classes just for that check.
>>
>> Regards,
>> Cheleswer


-- 
Bertrand Delsart,                     bertrand.delsart at oracle.com
Oracle,         180 av. de l'Europe,          ZIRST de Montbonnot
38334 Saint Ismier,                                        FRANCE
Phone : +33 4 76 18 81 23

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NOTICE: This email message is for the sole use of the intended
recipient(s) and may contain confidential and privileged
information. Any unauthorized review, use, disclosure or distribution
is prohibited. If you are not the intended recipient, please contact
the sender by reply email and destroy all copies of the original
message.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~