libmemstat
- library interface to retrieve kernel memory allocator statistics
LIBRARY
Lb libmemstat
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 *
Fo memstat_mtl_find
Fa struct memory_type_list *list int allocator const char *name
Fc Ft 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_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
Fo memstat_set_caller_pointer
Fa struct memory_type *mtp int index void *value
Fc Ft uint64_t
memstat_get_caller_uint64 (const struct memory_type *mtp int index); void
Fo memstat_set_caller_uint64
Fa struct memory_type *mtp int index uint64_t value
Fc Ft 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 *
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
memstat_get_percpu_free (const struct memory_type *mtp int cpu);
DESCRIPTION
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.
supports both retrieving a single statistics snapshot, as well as
incrementally updating statistics for long-term monitoring.
describes each memory type using a
Vt struct memory_type ,
an opaque memory type accessed by the application using accessor functions
in the library.
returns and updates chains of
Vt struct memory_type
via a
Vt 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.
Vt 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 Vt 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.
Caller Vt memory_type
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
MEMSTAT_MAXCALLER
Caller-owned fields are initialized to
0
or
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.
Allocator Types
Currently,
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
permittible from
memstat_mtl_find (.);
Access Method List
The following accessor methods are defined, of which some will be valid for
a given memory type:
Fn memstat_get_name
Return a pointer to the name of the memory type.
Memory for the name is owned by
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.
Fn memstat_get_allocator
Return an integer identifier for the memory allocator that owns the memory
type.
Fn memstat_get_countlimit
If the memory type has an administrative limit on the number of simultaneous
allocations, return it.
Fn memstat_get_byteslimit
If the memory type has an administrative limit on the number of bytes of
memory that may be simultaenously allocated for the memory type, return it.
Fn memstat_get_sizemask
If the memory type supports variable allocation sizes, return a bitmask of
sizes allocated for the memory type.
Fn memstat_get_size
If the memory type supports a fixed allocation size, return that size.
Fn memstat_get_memalloced
Return the total number of bytes allocated for the memory type over its
lifetime.
Fn memstat_get_memfreed
Return the total number of bytes freed for the memory type over its lifetime.
Fn memstat_get_numallocs
Return the total number of allocations for the memory type over its lifetime.
Fn memstat_get_numfrees
Return the total number of frees for the memory type over its lifetime.
Fn memstat_get_bytes
Return the current number of bytes allocated to the memory type.
Fn memstat_get_count
Return the current number of allocations for the memory type.
Fn memstat_get_free
If the memory allocator supports a cache, return the number of items in the
cache.
Fn memstat_get_failures
If the memory allocator and type permit allocation failures, return the
number of allocation failures measured.
Fn memstat_get_caller_pointer
Return a caller-owned pointer for the memory type.
Fn memstat_set_caller_pointer
Set a caller-owned pointer for the memory type.
Fn memstat_get_caller_uint64
Return a caller-owned integer for the memory type.
Fn memstat_set_caller_uint64
Set a caller-owned integer for the memory type.
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.
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.
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.
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.
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.
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.
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.
Fn memstat_get_percpu_caller_pointer
Return a caller-owned per-CPU pointer for the memory type.
Fn memstat_set_percpu_caller_pointer
Set a caller-owned per-CPU pointer for the memory type.
Fn memstat_get_percpu_caller_uint64
Return a caller-owned per-CPU integer for the memory type.
Fn memsttat_set_percpu_caller_uint64
Set a caller-owned per-CPU integer for the memory type.
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.
RETURN VALUES
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 .
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
Er 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
Er ENOMEM .
MEMSTAT_ERROR_VERSION
Returned if the current version of
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
Er EACCES
or
Er EPERM .
MEMSTAT_ERROR_TOOMANYCPUS
Returned if the compile-time limit on the number of CPUs in
is lower than the number of CPUs returned by a statistics data source.
MEMSTAT_ERROR_DATAERROR
Returned if
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
experiences an error while using
kvm(3)
interfaces to query statistics data.
Use
kvm_geterr3
to retrieve the error.
MEMSTAT_ERROR_KVM_NOSYMBOL
Returned if
is unable to read a required symbol from the kernel being operated on.
MEMSTAT_ERROR_KVM_SHORTREAD
Returned if
attempts to read data from a live memory image or kernel core dump and
insufficient data is returned.
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.
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);
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 .
BUGS
There are memory allocators in the kernel, such as the VM page allocator
and
sf_buf
allocator, which are not currently supported by
.
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.
