mmap performance and memory use
marktinguely at gmail.com
Tue Oct 11 18:01:38 UTC 2011
On 10/11/2011 11:12 AM, Alan Cox wrote:
> On 10/10/2011 16:28, Wojciech Puchar wrote:
>> is it possible to force VM subsystem to operate on superpages when
>> possible - i mean swapping in 2MB chunks?
> Currently, no. For some applications, like the Sun/Oracle JVM, that
> have code to explicitly manage large pages, there could be some
> benefit in the form of reduced overhead. So, it's on my "to do" list,
> but no where near the top of that list.
Am I correct in remembering that super-pages have to be aligned on the
super-page boundary and be contiguous?
If so, in the mmap(), he may want to include the 'MAP_FIXED' flag with
an address that is on a super-page boundary. Right now, the
"VMFS_ALIGNED_SPACE" that does the VA super-page alignment is only used
for device pagers.
Similarly, if the allocated physical pages for the object are not
contiguous, then MAP_PREFAULT_READ will not result in a super-page
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