Include other sources of freeable memory in the freemem calculation

Prevents ARC collapse when non-ZFS filesystems, the block layer or other
memory consumers use a lot of reclaimable memory in the page cache.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes zfsonlinux/zfs#3680
Closes #471

diff --git a/include/sys/vmsystm.h b/include/sys/vmsystm.h
index 2fa169523ddfd0efa6a2768301bd707108681240..9d334fe0a16e7bcf04bbdb61be80eaedf596f651 100644 (file)
--- a/include/sys/vmsystm.h
+++ b/include/sys/vmsystm.h
@@ -35,7 +35,10 @@
 
 #define        membar_producer()               smp_wmb()
 #define        physmem                         totalram_pages
-#define        freemem                         nr_free_pages()
+#define        freemem                 (nr_free_pages() + \
+                               global_page_state(NR_INACTIVE_FILE) + \
+                               global_page_state(NR_INACTIVE_ANON) + \
+                               global_page_state(NR_SLAB_RECLAIMABLE))
 
 #define        xcopyin(from, to, size)         copy_from_user(to, from, size)
 #define        xcopyout(from, to, size)        copy_to_user(to, from, size)