Matthew Ahrens 8fbf432ae2 anon_pages are not free/evictable ... `arc_free_memory()` returns the amount of memory that the ARC considers to be free. This includes pages that are not actually free, but can be evicted with essentially zero cost (without doing any i/o), for example the page cache. The ARC can "squeeze out" any pages included in this calculation, leaving only `arc_sys_free` (1/64th of RAM) for these free/evictable pages. Included in the count of free/evictable pages is `nr_inactive_anon_pages()`, which is described as "Anonymous memory that has not been used recently and can be swapped out". These pages would have to be written out to disk (swap) in order to evict them, and they are not included in `/proc/meminfo`'s `MemAvailable`. Therefore it is not appropriate for `nr_inactive_anon_pages()` to be included in the free/evictable memory returned by `arc_free_memory()`, because the ARC shouldn't (intentionally) make the system swap. This commit removes `nr_inactive_anon_pages()` from the memory returned by `arc_free_memory()`. This is a step towards enabling the ARC to manage free memory by monitoring it and reducing the ARC size as we notice that there is insufficient free memory (in the `arc_reap_zthr`), rather than the current method of relying on the `arc_shrinker` callback. Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com> Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10575		2020-07-16 10:11:26 -07:00
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spl	Fix early include of <linux/percpu_compat.h>	2020-07-15 15:58:15 -07:00
zfs	anon_pages are not free/evictable	2020-07-16 10:11:26 -07:00