What is the default value of vm.zone_reclaim_mode in Red Hat Enterprise Linux 5 ?

Solution Unverified - Updated -

Environment

  • Red Hat Enterprise Linux 5
  • vm.zone_reclaim_mode (mm)

Issue

  • What is the default zone_reclaim_mode values on RHEL-5.6, 5.7, 5.8 and 5.9 ?

Resolution

  • The default value of vm.zone_reclaim_mode tunable is 0 on RHEL-5.6, 5.7, 5.8 and 5.9.

Kernel Source: vmscan.c

         1614 int zone_reclaim_mode __read_mostly;           
         1615 
         1616 #define RECLAIM_OFF 0
         1617 #define RECLAIM_ZONE (1<<0)   /* Run shrink_cache on the zone */
         1618 #define RECLAIM_WRITE (1<<1)  /* Writeout pages during reclaim */
         1619 #define RECLAIM_SWAP (1<<2)   /* Swap pages out during reclaim */
         1620 
         1621 /*

Note: The value for vm.zone_reclaim_mode tunable is determined automatically per the numa distances at boot time.

Kernel Source: page_alloc.c

         1585   while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
         1586       int distance = node_distance(local_node, node);
         1587 
         1588       /*
         1589        * If another node is sufficiently far away then it is better
         1590        * to reclaim pages in a zone before going off node.
         1591        */
         1592       if (distance > RECLAIM_DISTANCE)
         1593           zone_reclaim_mode = 1;          
         1594 
         1595       /*

This solution is part of Red Hat’s fast-track publication program, providing a huge library of solutions that Red Hat engineers have created while supporting our customers. To give you the knowledge you need the instant it becomes available, these articles may be presented in a raw and unedited form.

Comments