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- ===============================
- Numa policy hit/miss statistics
- ===============================
- /sys/devices/system/node/node*/numastat
- All units are pages. Hugepages have separate counters.
- The numa_hit, numa_miss and numa_foreign counters reflect how well processes
- are able to allocate memory from nodes they prefer. If they succeed, numa_hit
- is incremented on the preferred node, otherwise numa_foreign is incremented on
- the preferred node and numa_miss on the node where allocation succeeded.
- Usually preferred node is the one local to the CPU where the process executes,
- but restrictions such as mempolicies can change that, so there are also two
- counters based on CPU local node. local_node is similar to numa_hit and is
- incremented on allocation from a node by CPU on the same node. other_node is
- similar to numa_miss and is incremented on the node where allocation succeeds
- from a CPU from a different node. Note there is no counter analogical to
- numa_foreign.
- In more detail:
- =============== ============================================================
- numa_hit A process wanted to allocate memory from this node,
- and succeeded.
- numa_miss A process wanted to allocate memory from another node,
- but ended up with memory from this node.
- numa_foreign A process wanted to allocate on this node,
- but ended up with memory from another node.
- local_node A process ran on this node's CPU,
- and got memory from this node.
- other_node A process ran on a different node's CPU
- and got memory from this node.
- interleave_hit Interleaving wanted to allocate from this node
- and succeeded.
- =============== ============================================================
- For easier reading you can use the numastat utility from the numactl package
- (http://oss.sgi.com/projects/libnuma/). Note that it only works
- well right now on machines with a small number of CPUs.
- Note that on systems with memoryless nodes (where a node has CPUs but no
- memory) the numa_hit, numa_miss and numa_foreign statistics can be skewed
- heavily. In the current kernel implementation, if a process prefers a
- memoryless node (i.e. because it is running on one of its local CPU), the
- implementation actually treats one of the nearest nodes with memory as the
- preferred node. As a result, such allocation will not increase the numa_foreign
- counter on the memoryless node, and will skew the numa_hit, numa_miss and
- numa_foreign statistics of the nearest node.
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