>>>>> "chris" == Chris Mason <mason@suse.com> writes:
Hi
chris> I'm not partial to how the actually memory pressure subsystem works, but I
chris> do like the idea of putting it in the address space operations. It just
chris> seems right, memory pressure goes against adress spaces.
Chris, I think that you don't want to put that in the address space
operations, the main reason is that you don't want your pages to stay
in the main LRU queue, because you need to freed them in an specific
order (not LRU at all). Then if shrink_mmap is not scanning your
pages, it is better to use your own reclaim function, that would be
called from do_try_to_free_pages (a la shrink_[di]cache way).
chris> Plus, it allows more flexibility later on...the log really should be an
chris> address space of its own, and the pressure should be applied against the
chris> log, not the FS. Think of multiple filesystems to a log, or multiple
chris> logs in a filesystem. Yes, these are ideas for 2.5 ;-)
This reason _completely_ convinces me that you want something like one
reclaim_cache function. Notice that otherwise you will be called more
times that you want to be called. If you put your pages in the main
LRU and you put a function in the address space, that function will be
called each time that one of *your* pages is scaned. That means that
if your function is called in one moment, and the next page also
belongs to your address space, you are getting *too* much pressure.
Later, Juan.
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