- min_unmapped_ratio
- min_slab_ratio
- panic_on_oom
+- mmap_min_address
+- numa_zonelist_order
==============================================================
dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
-block_dump, swap_token_timeout, drop-caches:
+block_dump, swap_token_timeout, drop-caches,
+hugepages_treat_as_movable:
See Documentation/filesystems/proc.txt
zone_reclaim_mode:
-Zone_reclaim_mode allows to set more or less agressive approaches to
+Zone_reclaim_mode allows someone to set more or less aggressive approaches to
reclaim memory when a zone runs out of memory. If it is set to zero then no
zone reclaim occurs. Allocations will be satisfied from other zones / nodes
in the system.
panic_on_oom
-This enables or disables panic on out-of-memory feature. If this is set to 1,
-the kernel panics when out-of-memory happens. If this is set to 0, the kernel
-will kill some rogue process, called oom_killer. Usually, oom_killer can kill
-rogue processes and system will survive. If you want to panic the system
-rather than killing rogue processes, set this to 1.
+This enables or disables panic on out-of-memory feature.
+
+If this is set to 0, the kernel will kill some rogue process,
+called oom_killer. Usually, oom_killer can kill rogue processes and
+system will survive.
+
+If this is set to 1, the kernel panics when out-of-memory happens.
+However, if a process limits using nodes by mempolicy/cpusets,
+and those nodes become memory exhaustion status, one process
+may be killed by oom-killer. No panic occurs in this case.
+Because other nodes' memory may be free. This means system total status
+may be not fatal yet.
+
+If this is set to 2, the kernel panics compulsorily even on the
+above-mentioned.
The default value is 0.
+1 and 2 are for failover of clustering. Please select either
+according to your policy of failover.
+
+==============================================================
+
+mmap_min_addr
+
+This file indicates the amount of address space which a user process will
+be restricted from mmaping. Since kernel null dereference bugs could
+accidentally operate based on the information in the first couple of pages
+of memory userspace processes should not be allowed to write to them. By
+default this value is set to 0 and no protections will be enforced by the
+security module. Setting this value to something like 64k will allow the
+vast majority of applications to work correctly and provide defense in depth
+against future potential kernel bugs.
+
+==============================================================
+
+numa_zonelist_order
+
+This sysctl is only for NUMA.
+'where the memory is allocated from' is controlled by zonelists.
+(This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation.
+ you may be able to read ZONE_DMA as ZONE_DMA32...)
+
+In non-NUMA case, a zonelist for GFP_KERNEL is ordered as following.
+ZONE_NORMAL -> ZONE_DMA
+This means that a memory allocation request for GFP_KERNEL will
+get memory from ZONE_DMA only when ZONE_NORMAL is not available.
+
+In NUMA case, you can think of following 2 types of order.
+Assume 2 node NUMA and below is zonelist of Node(0)'s GFP_KERNEL
+
+(A) Node(0) ZONE_NORMAL -> Node(0) ZONE_DMA -> Node(1) ZONE_NORMAL
+(B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA.
+
+Type(A) offers the best locality for processes on Node(0), but ZONE_DMA
+will be used before ZONE_NORMAL exhaustion. This increases possibility of
+out-of-memory(OOM) of ZONE_DMA because ZONE_DMA is tend to be small.
+
+Type(B) cannot offer the best locality but is more robust against OOM of
+the DMA zone.
+
+Type(A) is called as "Node" order. Type (B) is "Zone" order.
+
+"Node order" orders the zonelists by node, then by zone within each node.
+Specify "[Nn]ode" for zone order
+
+"Zone Order" orders the zonelists by zone type, then by node within each
+zone. Specify "[Zz]one"for zode order.
+
+Specify "[Dd]efault" to request automatic configuration. Autoconfiguration
+will select "node" order in following case.
+(1) if the DMA zone does not exist or
+(2) if the DMA zone comprises greater than 50% of the available memory or
+(3) if any node's DMA zone comprises greater than 60% of its local memory and
+ the amount of local memory is big enough.
+Otherwise, "zone" order will be selected. Default order is recommended unless
+this is causing problems for your system/application.
projects / karo-tx-linux.git / blobdiff