Review request: (turn off transparent huge pages) 8024838: Significant slowdown due to transparent huge pages
stefan.karlsson at oracle.com
Fri Oct 11 13:51:37 PDT 2013
On 10/11/13 10:32 PM, Andrew Hughes wrote:
> ----- Original Message -----
>> Please review this change to turn off transparent huge pages by default.
>> 8024838: Significant slowdown due to transparent huge pages
>> Summary: Don't turn on transparent huge pages
>> (-XX:+UseTransparentHugePages) unless explicitly specified on the
>> command line. This has the effect that large pages are never turned on
>> Linux unless the user has explicitly enabled any of the large pages
>> flags: -XX:+UseLargePages, -XX:+UseTransparentHugePages,
>> -XX:+UseHugeTLBFS, and -XX:+UseSHM.
>> Reviewed-by: TBD1, TBD2
> Can you explain where you see this slowdown?
One of the issues are described in the bug:
There's another issues we're Nashorn runs 10% slower with CompressedOops
turned on, most likely due to THP in the Compressed Class Space. That
bug is marked Confidential, so I can't give you a link. =(
Another issue is the extra memory usage for small work loads. That bug
is, apparently, also marked Confidential.
> I'm a little worried that
> this does not seem to have been questioned in this review.
Turning transparent huge pages on by default was done prematurely. If we
do more performance evaluations in the future, this decision could be
If anyone still wants large pages they are free to use either of:
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