Linked by Thom Holwerda on Wed 28th Feb 2007 19:29 UTC
Jeff Atwood explains why Vista uses so much memory. "You have to stop thinking of system memory as a resource and start thinking of it as a a cache. Just like the level 1 and level 2 cache on your CPU, system memory is yet another type of high-speed cache that sits between your computer and the disk drive. And the most important rule of cache design is that empty cache memory is wasted cache memory. Empty cache isn't doing you any good. It's expensive, high-speed memory sucking down power for zero benefit. The primary mission in the life of every cache is to populate itself as quickly as possible with the data that's most likely to be needed - and to consistently deliver a high 'hit rate' of needed data retrieved from the cache."
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Member since:
2005-07-08
First, I can't possibly figure out how that "it" I replaced could refer to SuperFetch or any similar technology because Linux doesn't have anticipatory page-in mechanism. Not in 2.4, not now, and probably not in the near future. In addition, memory is not a cache for paging space, so any attempt to associate SuperFetch with using memory as a disk cache is simply wrong.
SuperFetch has nothing to do with the disk cache, since it doesn't have anything to do with the filesystem. On the contrary, it is a virtual memory mechanism. It performs page-ins from the paging space before the virtual pages are referenced based on previously observed trends, replacing least-recently-used pages in memory with hopefully soon-to-be-used pages from paging space. SuperFetch doesn't change the fact that memory should always be full, nor does it create a magic way to page something in without paging something out. It doesn't minimize paging, either. In the best case scenario, it performs paging earlier than it would have otherwise occurred. In anything but the best case, it generates more paging operations than necessary.
I don't understand why you take offense to my comment. Anyone can argue the point of the article, but not that many people actually have the knowledge to decide for themselves whether the whole premise of the article is full of crap. I assumed that the article must be about a disk cache, since that's the only way the teaser makes sense. Memory is not a cache for paging space! When a page gets copied into memory, its blocks are freed on the disk's paging space. When filesystem data gets cached, it persists on the backing store. The whole premise of the article is wrong. So why should I argue it?