RFR (L): 8058354: SPECjvm2008-Derby -2.7% performance regression on Solaris-X64 starting with 9-b29

Thomas Schatzl thomas.schatzl at oracle.com
Tue Feb 3 00:06:08 UTC 2015


Some correction:

On Mon, 2015-02-02 at 17:58 +0100, Thomas Schatzl wrote:
> Hi,
> 
>   there have been multiple questions about this because my explanation
> was too confusing. Sorry. I will try to clear this up in the following.
> 
> The main reason as to why there is the limitation of requiring large
> page alignment of auxiliary data structures is that it simplifies
> management of the pages a lot with lit
[...]
> 
> Another option (3) would be to always use small pages in the border
> areas between heap regions to avoid a single page in the BOT
> corresponding to some heap region.

Forget that option, that does not work, and does not make sense given
the context. A small page on the BOT corresponds to 2M on the heap, if
you have the wrong region size (e.g. 1M) you can never do that and need
to implement (2).
And large pages cover a too large area to split anything (1G).

This splitting stuff would only be an option if you allowed an unaligned
heap. We do not.

Sorry,
Thomas



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