Re: cp file /dev/zero <-> cache [was Re: increasing page size]

[ebiederm+eric@npwt.net (Eric W. Biederman)]

>>>>> "ST" == Stephen C Tweedie <sct@redhat.com> writes:

ST> It does: the Duff's device in try_to_free_page does it, and seems to
ST> work well enough.  It was certainly tuned tightly enough: all of the
ST> hard part of getting the kswap stuff working well in try_to_swap_out()
ST> was to do with tuning the aggressiveness of swap relative to the buffer
ST> and cache reclaim mechanisms so that the try_to_free_page loop works
ST> well.  That's why the recent policies of adding little rules here and
ST> there all over the mm layer have disturbed the balance so much, I think.

The use of touch_page and age_page appear to be the most likely
canidates for the page cache being more persistent than it used to
be.

If I'm not mistaken shrink_mmap must be called more often now to
remove a given page.

Eric


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