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libmemstat.3
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memstat.c
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memstat.h
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memstat_uma.c
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Editing: libmemstat.3
.\" 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 February 11, 2014 .Dt LIBMEMSTAT 3 .Os .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 General Functions .Ft "const char *" .Fn memstat_strerror "int error" .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 *" .Fo memstat_mtl_find .Fa "struct memory_type_list *list" "int allocator" "const char *name" .Fc .Ft void .Fn memstat_mtl_free "struct memory_type_list *list" .Ft int .Fn memstat_mtl_geterror "struct memory_type_list *list" .Ss Allocator Query Functions .Ft int .Fn memstat_kvm_all "struct memory_type_list *list" "void *kvm_handle" .Ft int .Fn memstat_kvm_malloc "struct memory_type_list *list" "void *kvm_handle" .Ft int .Fn memstat_kvm_uma "struct memory_type_list *list" "void *kvm_handle" .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_rsize "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 .Fo memstat_set_caller_pointer .Fa "struct memory_type *mtp" "int index" "void *value" .Fc .Ft uint64_t .Fn memstat_get_caller_uint64 "const struct memory_type *mtp" "int index" .Ft void .Fo memstat_set_caller_uint64 .Fa "struct memory_type *mtp" "int index" "uint64_t value" .Fc .Ft uint64_t .Fn memstat_get_zonefree "const struct memory_type *mtp" .Ft uint64_t .Fn memstat_get_kegfree "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 *" .Fo memstat_get_percpu_caller_pointer .Fa "const struct memory_type *mtp" "int cpu" "int index" .Fc .Ft void .Fo memstat_set_percpu_caller_pointer .Fa "struct memory_type *mtp" "int cpu" "int index" "void *value" .Fc .Ft uint64_t .Fo memstat_get_percpu_caller_uint64 .Fa "const struct memory_type *mtp" "int cpu" "int index" .Fc .Ft void .Fo memstat_set_percpu_caller_uint64 .Fa "struct memory_type *mtp" "int cpu" "int index" "uint64_t value" .Fc .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_kvm_all , .Fn memstat_kvm_malloc , .Fn memstat_kvm_uma , .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. If an error is detected during a query call, error condition information may be retrieved using .Fn memstat_mtl_geterror , and converted to a user-readable string using .Fn memstat_strerror . .Pp 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 Vt memory_type Ss 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 Caller Vt memory_type Ss Fields .Vt "struct memory_type" includes fields to allow the application to store data, in the form of pointers and 64-bit integers, with memory types. 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. General and per-CPU storage is provided with each .Vt "struct memory_type" in the form of an array of pointers and integers. The array entries are accessed via the .Fa index argument to the get and set accessor methods. Possible values of .Fa index range between 0 and .Dv MEMSTAT_MAXCALLER . .Pp Caller-owned fields are initialized to 0 or .Dv NULL when a new .Vt "struct memory_type" is allocated and attached to a memory type list; these fields retain their values across queries that update library-owned fields. .Ss Allocator Types Currently, .Nm supports two kernel allocators: .Dv ALLOCATOR_UMA for .Xr uma 9 , and .Dv ALLOCATOR_MALLOC for .Xr malloc 9 . These values may be passed to .Fn memstat_mtl_find , and will be returned by .Fn memstat_get_allocator . Two additional constants in the allocator name space are defined: .Dv ALLOCATOR_UNKNOWN , which will only be returned as a result of a library error, and .Dv ALLOCATOR_ANY , which can be used to specify that returning types matching any allocator is permittable from .Fn memstat_mtl_find . .Ss Access Method List The following accessor methods are defined, of which some will be valid for a given memory type: .Bl -tag -width indent .It Fn memstat_get_name Return a pointer to the name of the memory type. Memory for the name is owned by .Nm and will be valid through a call to .Fn memstat_mtl_free . Note that names will be unique with respect to a single allocator, but that the same name might be used by different memory types owned by different memory allocators. .It Fn memstat_get_allocator Return an integer identifier for the memory allocator that owns the memory type. .It Fn memstat_get_countlimit If the memory type has an administrative limit on the number of simultaneous allocations, return it. .It Fn memstat_get_byteslimit If the memory type has an administrative limit on the number of bytes of memory that may be simultaneously allocated for the memory type, return it. .It Fn memstat_get_sizemask If the memory type supports variable allocation sizes, return a bitmask of sizes allocated for the memory type. .It Fn memstat_get_size If the memory type supports a fixed allocation size, return that size. .It Fn memstat_get_rsize If the memory type supports a fixed allocation size, return real size of an allocation. Real size can exceed requested size due to alignment constraints or implicit padding. .It Fn memstat_get_memalloced Return the total number of bytes allocated for the memory type over its lifetime. .It Fn memstat_get_memfreed Return the total number of bytes freed for the memory type over its lifetime. .It Fn memstat_get_numallocs Return the total number of allocations for the memory type over its lifetime. .It Fn memstat_get_numfrees Return the total number of frees for the memory type over its lifetime. .It Fn memstat_get_bytes Return the current number of bytes allocated to the memory type. .It Fn memstat_get_count Return the current number of allocations for the memory type. .It Fn memstat_get_free If the memory allocator supports a cache, return the number of items in the cache. .It Fn memstat_get_failures If the memory allocator and type permit allocation failures, return the number of allocation failures measured. .It Fn memstat_get_caller_pointer Return a caller-owned pointer for the memory type. .It Fn memstat_set_caller_pointer Set a caller-owned pointer for the memory type. .It Fn memstat_get_caller_uint64 Return a caller-owned integer for the memory type. .It Fn memstat_set_caller_uint64 Set a caller-owned integer for the memory type. .It Fn memstat_get_zonefree If the memory allocator supports a multi-level allocation structure, return the number of cached items in the zone. These items will be in a fully constructed state available for immediate use. .It Fn memstat_get_kegfree If the memory allocator supports a multi-level allocation structure, return the number of cached items in the keg. These items may be in a partially constructed state, and may require further processing before they can be made available for use. .It Fn memstat_get_percpu_memalloced If the memory allocator supports per-CPU statistics, return the number of bytes of memory allocated for the memory type on the CPU over its lifetime. .It Fn memstat_get_percpu_memfreed If the memory allocator supports per-CPU statistics, return the number of bytes of memory freed from the memory type on the CPU over its lifetime. .It Fn memstat_get_percpu_numallocs If the memory allocator supports per-CPU statistics, return the number of allocations for the memory type on the CPU over its lifetime. .It Fn memstat_get_percpu_numfrees If the memory allocator supports per-CPU statistics, return the number of frees for the memory type on the CPU over its lifetime. .It Fn memstat_get_percpu_sizemask If the memory allocator supports variable size memory allocation and per-CPU statistics, return the size bitmask for the memory type on the CPU. .It Fn memstat_get_percpu_caller_pointer Return a caller-owned per-CPU pointer for the memory type. .It Fn memstat_set_percpu_caller_pointer Set a caller-owned per-CPU pointer for the memory type. .It Fn memstat_get_percpu_caller_uint64 Return a caller-owned per-CPU integer for the memory type. .It Fn memstat_set_percpu_caller_uint64 Set a caller-owned per-CPU integer for the memory type. .It Fn memstat_get_percpu_free If the memory allocator supports a per-CPU cache, return the number of free items in the per-CPU cache of the designated CPU. .El .Sh RETURN VALUES .Nm functions fall into three categories: functions returning a pointer to an object, functions returning an integer return value, and functions implementing accessor methods returning data from a .Vt "struct memory_type" . .Pp Functions returning a pointer to an object will generally return .Dv NULL on failure. .Fn memstat_mtl_alloc will return an error value via .Va errno , which will consist of the value .Er ENOMEM . Functions .Fn memstat_mtl_first , .Fn memstat_mtl_next , and .Fn memstat_mtl_find will return .Dv NULL when there is no entry or match in the list; however, this is not considered a failure mode and no error value is available. .Pp Functions returning an integer success value will return 0 on success, or \-1 on failure. If a failure is returned, the list error access method, .Fn memstat_mtl_geterror , may be used to retrieve the error state. The string representation of the error may be retrieved using .Fn memstat_strerror . Possible error values are: .Bl -tag -width ".Dv MEMSTAT_ERROR_KVM_SHORTREAD" .It Dv MEMSTAT_ERROR_UNDEFINED Undefined error. Occurs if .Fn memstat_mtl_geterror is called on a list before an error associated with the list has occurred. .It Dv MEMSTAT_ERROR_NOMEMORY Insufficient memory. Occurs if library calls to .Xr malloc 3 fail, or if a system call to retrieve kernel statistics fails with .Er ENOMEM . .It Dv MEMSTAT_ERROR_VERSION Returned if the current version of .Nm is unable to interpret the statistics data returned by the kernel due to an explicit version mismatch, or to differences in data structures that cannot be reconciled. .It Dv MEMSTAT_ERROR_PERMISSION Returned if a statistics source returns .Va errno values of .Er EACCES or .Er EPERM . .It Dv MEMSTAT_ERROR_DATAERROR Returned if .Nm is unable to interpret statistics data returned by the data source, even though there does not appear to be a version problem. .It Dv MEMSTAT_ERROR_KVM Returned if .Nm experiences an error while using .Xr kvm 3 interfaces to query statistics data. Use .Xr kvm_geterr 3 to retrieve the error. .It Dv MEMSTAT_ERROR_KVM_NOSYMBOL Returned if .Nm is unable to read a required symbol from the kernel being operated on. .It Dv MEMSTAT_ERROR_KVM_SHORTREAD Returned if .Nm attempts to read data from a live memory image or kernel core dump and insufficient data is returned. .El .Pp Finally, functions returning data from a .Vt "struct memory_type" pointer are not permitted to fail, and directly return either a statistic or pointer to a string. .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\en", (unsigned long long)mbuf_count); .Ed .Sh SEE ALSO .Xr malloc 9 , .Xr uma 9 .Sh HISTORY The .Nm 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 Mt rwatson@FreeBSD.org . .Sh BUGS There are memory allocators in the kernel, such as the VM page allocator and .Nm sf_buf allocator, which are not currently supported by .Nm . .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.
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