Re: Q: PAGE_CACHE_SIZE?
Emil Briggs (briggs@bucky.physics.ncsu.edu)
Thu, 27 May 1999 19:54:22 -0400 (EDT)
>
>> For large amounts of memory on fast boxes you want a higher page
>> size. Some vendors even pick page size based on memory size at
>> boot up.
>
>This sounds suspiciously like the 'larger-blocks-for-larger-FSes'
>tactic other systems have been using to hide the bad scalability
>of their algorithms.
>
>A larger page size is no compensation for the lack of a decent
>read-{ahead,back,anywhere} I/O clustering algorithm in the OS.
>I believe we should take the more appropriate path and build
>a proper 'smart' algorithm. Once we're optimizing for I/O
>minimization, CPU is relatively cheap anyway...
>
Another reason for large page sizes has nothing to do with I/O. On
an architecture where TLB misses are expensive (e.g the Origin2000)
a larger page size can have a big effect on performance for
applications that access a lot of memory. Running one numerical
simulation that I use on the O2K with 16K pages is around 20% slower
than running it using 64K pages.
Regards
Emil
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