statistics via a binary structure stream:
- Add structure 'uma_stream_header', which defines a stream version,
definition of MAXCPUs used in the stream, and the number of zone
records in the stream.
- Add structure 'uma_type_header', which defines the name, alignment,
size, resource allocation limits, current pages allocated, preferred
bucket size, and central zone + keg statistics.
- Add structure 'uma_percpu_stat', which, for each per-CPU cache,
includes the number of allocations and frees, as well as the number
of free items in the cache.
- When the sysctl is queried, return a stream header, followed by a
series of type descriptions, each consisting of a type header
followed by a series of MAXCPUs uma_percpu_stat structures holding
per-CPU allocation information. Typical values of MAXCPU will be
1 (UP compiled kernel) and 16 (SMP compiled kernel).
This query mechanism allows user space monitoring tools to extract
memory allocation statistics in a machine-readable form, and to do so
at a per-CPU granularity, allowing monitoring of allocation patterns
across CPUs in order to better understand the distribution of work and
memory flow over multiple CPUs.
While here, also export the number of UMA zones as a sysctl
vm.uma_count, in order to assist in sizing user swpace buffers to
receive the stream.
A follow-up commit of libmemstat(3), a library to monitor kernel memory
allocation, will occur in the next few days. This change directly
supports converting netstat(1)'s "-mb" mode to using UMA-sourced stats
rather than separately maintained mbuf allocator statistics.
MFC after: 1 week
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