Re: [RFC] prefault optimization

["Martin J. Bligh" <mbligh@aracnet.com>]

>> 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

The patch is designed to only prefault in pages which are already in the
pagecache, so it should be pretty cheap. I'd agree that faulting in all
the pages from disk would be too expensive.

M.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"aart@kvack.org"> aart@kvack.org </a>