cpghost cpghost at
Thu May 28 15:17:43 UTC 2009

On Thu, May 28, 2009 at 02:50:16PM +0200, Wojciech Puchar wrote:
> maybe not new news but i just found this:
> It says about pages 4KB and 4MB and that it's done 
> automatically.
> Two questions:
> 1) is it on all architectures including amd64? As amd64 supports 4KB, 2MB 
> and 1GB pages it sounds inconsistent with the above.
> 2) how does this "automatic" selection work. By just having program with 
> large continous data space (like squid proxy) will it put that data on 2MB 
> pages.

The following excerpt from:
may be helpful:

  [amd64, i386] The FreeBSD virtual memory subsystem now supports
  fully transparent use of superpages for application memory;
  application memory pages are dynamically promoted to or demoted from
  superpages without any modification to application code. This change
  offers the benefit of large page sizes such as improved virtual
  memory efficiency and reduced TLB (translation lookaside buffer)
  misses without downsides like application changes and virtual memory
  inflexibility. This is disabled by default and can be enabled by
  setting a loader tunable vm.pmap.pg_ps_enabled to 1.

> if it's true i would be enough reason to upgrade to 7.2 on 2 computers.


Cordula's Web.

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