Linked by Thom Holwerda on Mon 11th May 2009 20:43 UTC
Windows SuperFetch is a technology in Windows Vista and onwards that is often misunderstood. I decided to delve into this technology to see what it is all about, and to dispel some of the myths surrounding this feature.
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kerframil
Member since:
2005-07-13

"Superfetch loads things in memory it thinks you'll need. If you don't need it, no harm done - 'unloading' doesn't exist. Apps start as fast as without superfetch OR faster. Never slower. Same story with the linux memory management, expect that the linux one is less smart."

Nonsense. The way Linux uses caching is much, much smarter, IMHO. It does moderate caching, leaving much of the system RAM free. This means less disc I/O, less flushing, less paging, but also faster load time for common apps, and faster access time for common data.

Now that is complete nonsense. Linux will gladly consume almost all available physical RAM for its pagecache. Case in point ... I have a Linux 2.6.28.9 system with 8G of RAM which has been up for 11 days. It currently has only 69M of RAM unused, with 637M used by applications, 523M used for kernel buffers (largely attributable to the ext4 inode cache in my case) and 6750M cached! In other words, the pagecache grows as large as it possibly can and that's a good thing.

That it does not on your PCLinuxOS system is due to an insufficient workload being generated for the pagecache to ever consume the majority of your available RAM and/or the kernel not running long enough before being shut down.

And, guess what, Windows works in the same way and there's nothing wrong with that. Indeed, it's hugely beneficial and the reason why a RAM upgrade yields immediate performance enhancements (even beyond the scope of providing for any especially memory hungry applications that may be used):

http://en.wikipedia.org/wiki/Page_cache#Memory_conservation

As the original poster alluded to, SuperFetch is a different kettle of fish. By virtue of the very nature of SuperFetch, the comment that the Linux VM is "less smart" is correct, as there is no equivalent to SuperFetch (please also note that "less smart" does not mean the same thing as "ineffective"). However, one could argue as to whether SuperFetch is worthwhile which, ultimately, is the topic under discussion here ;)

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