A general caching filesystem [LWN.net]

A general caching filesystem

Posted Sep 14, 2004 2:13 UTC (Tue) by xoddam (subscriber, #2322)
Parent article: A general caching filesystem

This seems to me like a really complicated reimplementation of virtual
memory.

All filesystems already use VM pages for caching, don't they?
I'd have thought that attaching backing store to those pages would have
been a much simpler task than writing a whole new cache interface.

But then I'm not really a filesystem hacker.

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A general caching filesystem

Posted Oct 25, 2004 0:55 UTC (Mon) by jcm (subscriber, #18262) [Link]

xoddam writes:

> This seems to me like a really complicated reimplementation of
> virtual memory.

No it's really not. By virtual memory your are referring to an aspect of VM implementations known as paging, and that in itself only really impacts upon so called ``anonymous memory''. There is a page cache for certain regular filesystems but it's not possible for all filesystems to exploit the page cache to full effect and in any case this patch adds the ability to use a local disk as an additional cache storage for even slower stuff like network mounted filesystems - so the page cache can always sit between this disk and user processes which use it.

Jon.