Re: [RFC] prefault optimization

[Mel Gorman <mel@csn.ul.ie>]

On Thu, 7 Aug 2003, Adam Litke wrote:

> This patch attempts to reduce page fault overhead for mmap'd files.  All
> pages in the page cache that will be managed by the current vma are
> instantiated in the page table.

I believe this could punish applications which use large numbers of shared
libraries, especially if only a small portion of library code is used.
Take something like konqueror which maps over 30 shared libraries. With
prefaulting, all the libraries will be fully faulted even if only a tiny
portion of some library code is used.  This, potentially, could put a lot
of unwanted pages into the page cache which will be a kick in the pants
for low-memory systems.

For example, I don't have audio enabled at all in konqueror, but with this
patch, it will fault in 77K of data for libaudio that won't be used.

Just my 2c

-- 
Mel Gorman
http://www.csn.ul.ie/~mel
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