Request for review (1 line) - 7186847

[Jon Masamitsu]

Mikael,

Thanks for the review.

I expect VirtualSpaceNodes to  grow
by VirtualSpaceSize which is 256k and
and that's where the use of large pages
will have an affect.  The Metachunks are
allocated out of the space in a
VirtualSpaceNode (the large VirtualSpaceNode
are divided up into chunks).  At least that's
what I'm expecting.

VirtualSpaceSize are actually smaller that
I thought they were so maybe those should
be large.  At least for 64bit.

Jon

On 10/8/2012 7:57 AM, Mikael Gerdin wrote:
> Jon,
>
> On 2012-10-06 00:12, Jon Masamitsu wrote:
>> 7186847: NPG: Use large pages for metadata allocations
>>
>> http://cr.openjdk.java.net/~jmasa/7186847/webrev.00/
>
> The fix makes sense, but I wonder how many of the allocations coming 
> in through the VirtualSpaceNode constructor are large enough to make 
> use of >4K pages?
> Since medium chunks are 8K words it looks like only humongous 
> allocations will cause large pages to be allocated. Are humongous 
> metaspace allocations even common enough to warrant the increased 
> "complexity" of the code?
> I'm not saying that your fix is making the code itself more complex, 
> but it may be misleading people reading it into thinking that large 
> page size allocations are being used when actually they are not.
>
> /Mikael
>
>>
>> Thanks.
>>
>> Jon
>