Add libmemstat(3), a library for use by debugging and monitoring

applications in tracking kernel memory statistics.  It provides an
abstracted interface to uma(9) and malloc(9) statistics, wrapped
around the recently added binary stream sysctls for the allocators.

Using this interface, it is easy to build monitoring tools, query
specific memory types for usage information, etc.  Facilities are
provided for binding caller-provided data to memory types,
incremental updates of memory types, and queries that span multiple
allocators.

Support for additional allocators is (relatively) easy to add.

The API for libmemstat(3) will probably change some over time as
consumers are written, and requirements evolve.  It is written to
avoid encoding ABIs for data structure layout into consuming
applications for this reason.

MFC after:	1 week

1 files changed, 238 insertions, 0 deletions

diff --git a/lib/libmemstat/libmemstat.3 b/lib/libmemstat/libmemstat.3
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+.\" Copyright (c) 2005 Robert N. M. Watson
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd June 27, 2005
+.Os
+.Dt LIBMEMSTAT 3
+.Sh NAME
+.Nm libmemstat
+.Nd "library interface to retrieve kernel memory allocator statistics"
+.Sh LIBRARY
+.Lb libmemstat
+.Sh SYNOPSIS
+.In sys/types.h
+.In memstat.h
+.Ss Memory Type List Management Functions
+.Ft struct memory_type_list *
+.Fn memstat_mtl_alloc "void"
+.Ft struct memory_type *
+.Fn memstat_mtl_first "struct memory_type_list *list"
+.Ft struct memory_type *
+.Fn memstat_mtl_next "struct memory_type *mtp"
+.Ft struct memory_type *
+.Fn memstat_mtl_find "struct memory_type_list *list" "int allocator" "const char *name"
+.Ft void
+.Fn memstat_mtl_free "struct memory_type_list *list"
+.Ss Allocator Query Functions
+.Ft int
+.Fn memstat_sysctl_all "struct memory_type_list *list" "int flags"
+.Ft int
+.Fn memstat_sysctl_malloc "struct memory_type_list *list" "int flags"
+.Ft int
+.Fn memstat_sysctl_uma "struct memory_type_list *list" "int flags"
+.Ss Memory Type Accessor Methods
+.Ft const char *
+.Fn memstat_get_name "const struct memory_type *mtp"
+.Ft int
+.Fn memstat_get_allocator "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_countlimit "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_byteslimit "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_sizemask "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_size "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_memalloced "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_memfreed "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_numallocs "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_numfrees "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_bytes "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_count "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_free "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_failures "const struct memory_type *mtp"
+.Ft void *
+.Fn memstat_get_caller_pointer "const struct memory_type *mtp" "int index"
+.Ft void
+.Fn memstat_set_caller_pointer "struct memory_type *mtp" "int index" "void *value"
+.Ft uint64_t
+.Fn memstat_get_caller_uint64 "const struct memory_type *mtp" "int index"
+.Ft void
+.Fn memstat_set_caller_uint64 "struct memory_type *mtp" "int index" "uint64_t value"
+.Ft uint64_t
+.Fn memstat_get_zonefree "const struct memory_type *mtp"
+.Ft uint64_t
+.Fn memstat_get_percpu_memalloced "const struct memory_type *mtp" "int cpu"
+.Ft uint64_t
+.Fn memstat_get_percpu_memfreed "const struct memory_type *mtp" "int cpu"
+.Ft uint64_t
+.Fn memstat_get_percpu_numallocs "const struct memory_type *mtp" "int cpu"
+.Ft uint64_t
+.Fn memstat_get_percpu_numfrees "const struct memory_type *mtp" "int cpu"
+.Ft uint64_t
+.Fn memstat_get_percpu_sizemask "const struct memory_type *mtp" "int cpu"
+.Ft void *
+.Fn memstat_get_percpu_caller_pointer "const struct memory_type *mtp" "int cpu" "int index"
+.Ft void
+.Fn memstat_set_percpu_caller_pointer "struct memory_type *mtp" "int cpu" "int index" "void *value"
+.Ft uint64_t
+.Fn memstat_get_percpu_caller_uint64 "const struct memory_type *mtp" "int cpu" "int index"
+.Ft void
+.Fn memstat_set_percpu_caller_uint64 "struct memory_type *mtp" "int cpu" "int index" "uint64_t value"
+.Ft uint64_t
+.Fn memstat_get_percpu_free "const struct memory_type *mtp" "int cpu"
+.Sh DESCRIPTION
+.Nm
+provides an interface to retrieve kernel memory allocator statistics, for
+the purposes of debugging and system monitoring, insulating applications
+from implementation details of the allocators, and allowing a tool to
+transparently support multiple allocators.
+.Nm
+supports both retrieving a single statistics snapshot, as well as
+incrementally updating statistics for long-term monitoring.
+.Pp
+.Nm
+describes each memory type using a
+.Vt struct memory_type ,
+an opaque memory type accessed by the application using accessor functions
+in the library.
+.Nm
+returns and updates chains of
+.Vt struct memory_type
+via a
+.Vt struct memory_type_list ,
+which will be allocated by calling
+.Fn memstat_mtl_alloc ,
+and freed on completion using
+.Fn memstat_mtl_free .
+Lists of memory types are populated via calls that query the kernel for
+statistics information; currently:
+.Fn memstat_sysctl_all ,
+.Fn memstat_sysctl_uma ,
+and
+.Fn memstat_sysctl_malloc .
+Repeated calls will incrementally update the list of memory types, permitting
+tracking over time without recreating all list state.
+Freeing the list will free all memory type data in the list, and so
+invalidates any outstanding pointers to entries in the list.
+.Vt struct memory_type
+entries in the list may be iterated over using
+.Fn memstat_mtl_first
+and
+.fn memstat_mtl_next ,
+which respectively return the first entry in a list, and the next entry in a
+list.
+.Fn memstat_mtl_find ,
+which will return a pointer to the first entry matching the passed
+parameters.
+.Pp
+A series of accessor methods is provided to access fields of the structure,
+including retrieving statistics and properties, as well as setting of caller
+owned fields.
+Direct application access to the data structure fields is not supported.
+.Ss Library memory_type Fields
+Each
+.Vt struct memory_type
+holds a description of the memory type, including its name and the allocator
+it is managed by, as well as current statistics on use.
+Some statistics are directly measured, others are derived from directly
+measured statistics.
+Certain high level statistics are present across all available allocators,
+such as the number of allocation and free operations; other measurements,
+such as the quantity of free items in per-CPU caches, or administrative
+limit on the number of allocations, is available only for specific
+allocators.
+.Ss User memory_type Fields
+.Vt struct memory_type
+includes fields appropriate for use by the application in order to more
+easily maintain state associated with memory types across updates.
+For example, the application author might make use of one of the caller
+pointers to reference a more complex data structure tracking long-term
+behavior of the memory type, or a window system object that is used to
+render the state of the memory type.
+Query updates may reset or otherwise modify all other fields in the
+.Vt struct memory_type
+data structure, but will preserve the caller-provided values, which will
+be initialized to
+.Dv 0
+or
+.Dv NULL
+before first use.
+.Sh EXAMPLES
+Create a memory type list, query the
+.Xr uma 9
+memory allocator for available statistics, and print out the number of
+allocations performed by the
+.Dv Mbuf
+zone.
+.Bd -literal -offset indent
+struct memory_type_list *mtlp;
+struct memory_type *mtp;
+uint64_t mbuf_count;
+
+mtlp = memstat_mtl_alloc();
+if (mtlp == NULL)
+    err(-1, "memstat_mtl_alloc");
+if (memstat_sysctl_uma(mtlp, 0) < 0)
+    err(-1, "memstat_sysctl_uma");
+mtp = memstat_mtl_find(mtlp, ALLOCATOR_UMA, "Mbuf");
+if (mtp == NULL)
+    errx(-1, "memstat_mtl_find: Mbuf not found");
+mbuf_count = memstat_get_count(mtp);
+memstat_mtl_free(mtlp);
+
+printf("Mbufs: %llu\\n", (unsigned long long)mbuf_count);
+.Ed
+.Sh SEE ALSO
+.Xr malloc 9 ,
+.Xr uma 9
+.Sh HISTORY
+The
+.Nm memstat
+library appeared in
+.Fx 6.0 .
+.Sh AUTHORS
+The kernel memory allocator changes necessary to support a general purpose
+monitoring library, along with the library, were written by
+.An Robert Watson Aq rwatson@FreeBSD.org
+.Sh BUGS
+.Nm
+cannot yet extract statistics from kernel core dumps, although this should be
+straight forward to implement.
+.Pp
+Once a memory type is present on a memory type list, it will not be removed
+even if the kernel no longer presents information on the type via its
+monitoring interfaces.
+In order to flush removed memory types, it is necessary to free the entire
+list and allocate a new one.