LIBMEMSTAT(3) FreeBSD Library Functions Manual LIBMEMSTAT(3)
NAME
libmemstat - library interface to retrieve kernel memory allocator
statistics
LIBRARY
Kernel Memory Allocator Statistics Library (libmemstat, -lmemstat)
SYNOPSIS
#include <sys/types.h>
#include <memstat.h>
General Functions
const char *
memstat_strerror(int error);
Memory Type List Management Functions
struct memory_type_list *
memstat_mtl_alloc(void);
struct memory_type *
memstat_mtl_first(struct memory_type_list *list);
struct memory_type *
memstat_mtl_next(struct memory_type *mtp);
struct memory_type *
memstat_mtl_find(struct memory_type_list *list, int allocator,
const char *name);
void
memstat_mtl_free(struct memory_type_list *list);
int
memstat_mtl_geterror(struct memory_type_list *list);
Allocator Query Functions
int
memstat_kvm_all(struct memory_type_list *list, void *kvm_handle);
int
memstat_kvm_malloc(struct memory_type_list *list, void *kvm_handle);
int
memstat_kvm_uma(struct memory_type_list *list, void *kvm_handle);
int
memstat_sysctl_all(struct memory_type_list *list, int flags);
int
memstat_sysctl_malloc(struct memory_type_list *list, int flags);
int
memstat_sysctl_uma(struct memory_type_list *list, int flags);
Memory Type Accessor Methods
const char *
memstat_get_name(const struct memory_type *mtp);
int
memstat_get_allocator(const struct memory_type *mtp);
uint64_t
memstat_get_countlimit(const struct memory_type *mtp);
uint64_t
memstat_get_byteslimit(const struct memory_type *mtp);
uint64_t
memstat_get_sizemask(const struct memory_type *mtp);
uint64_t
memstat_get_size(const struct memory_type *mtp);
uint64_t
memstat_get_rsize(const struct memory_type *mtp);
uint64_t
memstat_get_memalloced(const struct memory_type *mtp);
uint64_t
memstat_get_memfreed(const struct memory_type *mtp);
uint64_t
memstat_get_numallocs(const struct memory_type *mtp);
uint64_t
memstat_get_numfrees(const struct memory_type *mtp);
uint64_t
memstat_get_bytes(const struct memory_type *mtp);
uint64_t
memstat_get_count(const struct memory_type *mtp);
uint64_t
memstat_get_free(const struct memory_type *mtp);
uint64_t
memstat_get_failures(const struct memory_type *mtp);
void *
memstat_get_caller_pointer(const struct memory_type *mtp, int index);
void
memstat_set_caller_pointer(struct memory_type *mtp, int index,
void *value);
uint64_t
memstat_get_caller_uint64(const struct memory_type *mtp, int index);
void
memstat_set_caller_uint64(struct memory_type *mtp, int index,
uint64_t value);
uint64_t
memstat_get_zonefree(const struct memory_type *mtp);
uint64_t
memstat_get_kegfree(const struct memory_type *mtp);
uint64_t
memstat_get_percpu_memalloced(const struct memory_type *mtp, int cpu);
uint64_t
memstat_get_percpu_memfreed(const struct memory_type *mtp, int cpu);
uint64_t
memstat_get_percpu_numallocs(const struct memory_type *mtp, int cpu);
uint64_t
memstat_get_percpu_numfrees(const struct memory_type *mtp, int cpu);
uint64_t
memstat_get_percpu_sizemask(const struct memory_type *mtp, int cpu);
void *
memstat_get_percpu_caller_pointer(const struct memory_type *mtp, int cpu,
int index);
void
memstat_set_percpu_caller_pointer(struct memory_type *mtp, int cpu,
int index, void *value);
uint64_t
memstat_get_percpu_caller_uint64(const struct memory_type *mtp, int cpu,
int index);
void
memstat_set_percpu_caller_uint64(struct memory_type *mtp, int cpu,
int index, uint64_t value);
uint64_t
memstat_get_percpu_free(const struct memory_type *mtp, int cpu);
DESCRIPTION
libmemstat 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.
libmemstat supports both retrieving a single statistics snapshot, as well
as incrementally updating statistics for long-term monitoring.
libmemstat describes each memory type using a struct memory_type, an
opaque memory type accessed by the application using accessor functions
in the library. libmemstat returns and updates chains of struct
memory_type via a struct memory_type_list, which will be allocated by
calling memstat_mtl_alloc(), and freed on completion using
memstat_mtl_free(). Lists of memory types are populated via calls that
query the kernel for statistics information; currently:
memstat_kvm_all(), memstat_kvm_malloc(), memstat_kvm_uma(),
memstat_sysctl_all(), memstat_sysctl_uma(), and 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 memstat_mtl_geterror(), and converted to a user-readable
string using memstat_strerror().
Freeing the list will free all memory type data in the list, and so
invalidates any outstanding pointers to entries in the list. struct
memory_type entries in the list may be iterated over using
memstat_mtl_first() and memstat_mtl_next(), which respectively return the
first entry in a list, and the next entry in a list. memstat_mtl_find(),
which will return a pointer to the first entry matching the passed
parameters.
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.
Library memory_type Ss Fields
Each 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.
Caller memory_type Ss Fields
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 struct memory_type in the form of an array of pointers
and integers. The array entries are accessed via the index argument to
the get and set accessor methods. Possible values of index range between
0 and MEMSTAT_MAXCALLER.
Caller-owned fields are initialized to 0 or NULL when a new struct
memory_type is allocated and attached to a memory type list; these fields
retain their values across queries that update library-owned fields.
Allocator Types
Currently, libmemstat supports two kernel allocators: ALLOCATOR_UMA for
uma(9), and ALLOCATOR_MALLOC for malloc(9). These values may be passed
to memstat_mtl_find(), and will be returned by memstat_get_allocator().
Two additional constants in the allocator name space are defined:
ALLOCATOR_UNKNOWN, which will only be returned as a result of a library
error, and ALLOCATOR_ANY, which can be used to specify that returning
types matching any allocator is permittable from memstat_mtl_find().
Access Method List
The following accessor methods are defined, of which some will be valid
for a given memory type:
memstat_get_name()
Return a pointer to the name of the memory type. Memory for the
name is owned by libmemstat and will be valid through a call to
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.
memstat_get_allocator()
Return an integer identifier for the memory allocator that owns
the memory type.
memstat_get_countlimit()
If the memory type has an administrative limit on the number of
simultaneous allocations, return it.
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.
memstat_get_sizemask()
If the memory type supports variable allocation sizes, return a
bitmask of sizes allocated for the memory type.
memstat_get_size()
If the memory type supports a fixed allocation size, return that
size.
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.
memstat_get_memalloced()
Return the total number of bytes allocated for the memory type
over its lifetime.
memstat_get_memfreed()
Return the total number of bytes freed for the memory type over
its lifetime.
memstat_get_numallocs()
Return the total number of allocations for the memory type over
its lifetime.
memstat_get_numfrees()
Return the total number of frees for the memory type over its
lifetime.
memstat_get_bytes()
Return the current number of bytes allocated to the memory type.
memstat_get_count()
Return the current number of allocations for the memory type.
memstat_get_free()
If the memory allocator supports a cache, return the number of
items in the cache.
memstat_get_failures()
If the memory allocator and type permit allocation failures,
return the number of allocation failures measured.
memstat_get_caller_pointer()
Return a caller-owned pointer for the memory type.
memstat_set_caller_pointer()
Set a caller-owned pointer for the memory type.
memstat_get_caller_uint64()
Return a caller-owned integer for the memory type.
memstat_set_caller_uint64()
Set a caller-owned integer for the memory type.
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.
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.
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.
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.
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.
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.
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.
memstat_get_percpu_caller_pointer()
Return a caller-owned per-CPU pointer for the memory type.
memstat_set_percpu_caller_pointer()
Set a caller-owned per-CPU pointer for the memory type.
memstat_get_percpu_caller_uint64()
Return a caller-owned per-CPU integer for the memory type.
memstat_set_percpu_caller_uint64()
Set a caller-owned per-CPU integer for the memory type.
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.
RETURN VALUES
libmemstat 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 struct
memory_type.
Functions returning a pointer to an object will generally return NULL on
failure. memstat_mtl_alloc() will return an error value via errno, which
will consist of the value ENOMEM. Functions memstat_mtl_first(),
memstat_mtl_next(), and memstat_mtl_find() will return 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.
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,
memstat_mtl_geterror(), may be used to retrieve the error state. The
string representation of the error may be retrieved using
memstat_strerror(). Possible error values are:
MEMSTAT_ERROR_UNDEFINED Undefined error. Occurs if
memstat_mtl_geterror() is called on a
list before an error associated with the
list has occurred.
MEMSTAT_ERROR_NOMEMORY Insufficient memory. Occurs if library
calls to malloc(3) fail, or if a system
call to retrieve kernel statistics fails
with ENOMEM.
MEMSTAT_ERROR_VERSION Returned if the current version of
libmemstat 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.
MEMSTAT_ERROR_PERMISSION Returned if a statistics source returns
errno values of EACCES or EPERM.
MEMSTAT_ERROR_DATAERROR Returned if libmemstat is unable to
interpret statistics data returned by
the data source, even though there does
not appear to be a version problem.
MEMSTAT_ERROR_KVM Returned if libmemstat experiences an
error while using kvm(3) interfaces to
query statistics data. Use
kvm_geterr(3) to retrieve the error.
MEMSTAT_ERROR_KVM_NOSYMBOL Returned if libmemstat is unable to read
a required symbol from the kernel being
operated on.
MEMSTAT_ERROR_KVM_SHORTREAD Returned if libmemstat attempts to read
data from a live memory image or kernel
core dump and insufficient data is
returned.
Finally, functions returning data from a struct memory_type pointer are
not permitted to fail, and directly return either a statistic or pointer
to a string.
EXAMPLES
Create a memory type list, query the uma(9) memory allocator for
available statistics, and print out the number of allocations performed
by the mbuf zone.
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);
SEE ALSO
malloc(9), uma(9)
HISTORY
The libmemstat library appeared in FreeBSD 6.0.
AUTHORS
The kernel memory allocator changes necessary to support a general
purpose monitoring library, along with the library, were written by
Robert Watson <rwatson@FreeBSD.org>.
BUGS
There are memory allocators in the kernel, such as the VM page allocator
and sf_buf allocator, which are not currently supported by libmemstat.
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.
FreeBSD 13.1-RELEASE-p6 February 11, 2014 FreeBSD 13.1-RELEASE-p6
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