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SubjectRe: Page cache patch - less aggressive
Dr. Werner Fink wrote:
> During testing the new buffer code I found that find_candidate()
> called very often in refill_freelist() runs try_to_free_buffer()
> ... this seems to free the previous buffer pages allocated by
> grow_buffers() in refill_freelist() and leads to heavy swap I/O

find_candidate() only calls try_to_free_buffer() if the buffer size
doesn't match what it's looking for. Therefore it won't release the
buffer pages allocated by the previous grow_buffers().

However, if two tasks were simultaneously using refill_freelist to get
different sizes of buffers, they could end up releasing each other's
newly added buffers.
> Does any body know a simple fix for find_candidate() in the
> new buffer code to avoid this behaviour?

Glad you asked :-) I've found some bugs in refill_freelist() that could
explain the oopses people have been reporting. I'm working on a patch
and will post it later (hopefully today.)

-Bill

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