Hi all,
in utlk there is following paragraph which is confusing me..
Is it a case that pages belonging to user mode addr space are not
present in page cache?? What actually are the contents of page cache then?
Here is a para from utlk... please help me above issue.
Highlighted content is confusing me.
"Another heuristic rule regulates the behavior of the refill_inactive_zone(
) function. The LRU lists include two kinds of pages: those belonging to the
User Mode address spaces, and those included in the page cache that do not
belong to any User Mode process. As stated earlier, the PFRA should tend to
shrink the page cache while leaving in RAM the pages owned by the User Mode
processes. However, no fixed "golden rule" may yield good performance in
every scenario, thus the refill_inactive_zone( ) function relies on a swap
tendency heuristic value: it determines whether the function will move all
kinds of pages, or just the pages that do not belong to the User Mode
address
spaces.[*]<http://mail.google.com/mail/?view=page&name=gp&ver=sh3fib53pgpk#1152da6c2cc1a683_11521b89f3b345fb_understandlk-CHP-17-FN5>The
swap tendency value is computed by the function as follows:
[*] The name "swap tendency" is a bit misleading, because the pages in User
Mode address spaces can be swappable, syncable, or discardable. However, the
swap tendency value certainly controls the amount of swapping performed by
the PFRA, because almost all swappable pages belong to the User Mode address
spaces.
swap tendency = mapped ratio / 2 + distress + swappiness
The mapped ratio value is the percentage of pages in all memory zones that
belong to User Mode address spaces (sc->nr_mapped) with respect to the total
number of allocatable page frames. A high value of mapped_ratio means that
the dynamic memory is mostly used by User Mode processes, while a low value
means that it is mostly used by the page cache."
