focal (3) memkind.3.gz

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NAME

       memkind - Heap manager that enables allocations to memory with different properties.
       This header expose STANDARD and EXPERIMENTAL API. API Standards are described below in this man page.

SYNOPSIS

       #include <memkind.h>

       Link with -lmemkind

   EXPERIMENTAL API:
       HEAP MANAGEMENT:
       int memkind_posix_memalign(memkind_t kind, void **memptr, size_t alignment, size_t size);

       KIND MANAGEMENT:
       int  memkind_create_kind(memkind_memtype_t  memtype_flags, memkind_policy_t policy, memkind_bits_t flags,
       memkind_t *kind);

   STANDARD API:
       ERROR HANDLING:
       void memkind_error_message(int err, char *msg, size_t size);

       LIBRARY VERSION:
       int memkind_get_version();

       HEAP MANAGEMENT:
       void *memkind_malloc(memkind_t kind, size_t size);
       void *memkind_calloc(memkind_t kind, size_t num, size_t size);
       void *memkind_realloc(memkind_t kind, void *ptr, size_t size);
       void memkind_free(memkind_t kind, void *ptr);
       size_t memkind_malloc_usable_size(memkind_t kind, void *ptr);
       void *memkind_defrag_reallocate(memkind_t kind, void *ptr);
       memkind_t memkind_detect_kind(void *ptr);

       KIND CONFIGURATION MANAGEMENT:
       struct memkind_config *memkind_config_new();
       void memkind_config_delete(struct memkind_config *cfg);
       void memkind_config_set_path(struct memkind_config *cfg, const char *pmem_dir);
       void memkind_config_set_size(struct memkind_config *cfg, size_t pmem_size);
       void memkind_config_set_memory_usage_policy(struct memkind_config *cfg, memkind_mem_usage_policy policy);

       KIND MANAGEMENT:
       int memkind_create_pmem(const char *dir, size_t max_size, memkind_t *kind);
       int memkind_create_pmem_with_config(struct memkind_config *cfg, memkind_t *kind);
       int memkind_destroy_kind(memkind_t kind);
       int memkind_check_available(memkind_t kind);

       STATISTICS:
       int memkind_update_cached_stats(void);
       int memkind_get_stat(memkind_t kind, memkind_stat stat, size_t *value);

       DECORATORS:
       void memkind_malloc_pre(memkind_t *kind, size_t *size);
       void memkind_malloc_post(memkind_t kind, size_t size, void **result);
       void memkind_calloc_pre(memkind_t *kind, size_t *nmemb, size_t *size);
       void memkind_calloc_post(memkind_t kind, size_t nmemb, size_t size, void **result);
       void memkind_posix_memalign_pre(memkind_t *kind, void **memptr, size_t *alignment, size_t *size);
       void memkind_posix_memalign_post(memkind_t kind, void **memptr, size_t alignment, size_t size, int *err);
       void memkind_realloc_pre(memkind_t *kind, void **ptr, size_t *size);
       void memkind_realloc_post(memkind_t *kind, void *ptr, size_t size, void **result);
       void memkind_free_pre(memkind_t *kind, void **ptr);
       void memkind_free_post(memkind_t kind, void *ptr);

DESCRIPTION

       memkind_error_message() converts an error number err returned by a member of the memkind interface to  an
       error message msg where the maximum size of the message is passed by the size parameter.

       HEAP MANAGEMENT:
       The  functions  described  in  this  section define a heap manager with an interface modeled on the ISO C
       standard API's, except that the user must specify the kind of memory with  the  first  argument  to  each
       function.  See  the KINDS section below for a full description of the implemented kinds.  For file-backed
       kind of memory see memkind_create_pmem() or memkind_create_pmem_with_config().

       memkind_malloc() allocates size bytes of uninitialized memory of the specified kind.  The allocated space
       is  suitably  aligned  (after possible pointer coercion) for storage of any type of object. If size is 0,
       then memkind_malloc() returns NULL.

       memkind_calloc() allocates space for num objects each size bytes in length in  memory  of  the  specified
       kind.   The  result  is  identical  to  calling memkind_malloc() with an argument of num * size, with the
       exception that the allocated memory is explicitly initialized to zero bytes.  If num or size is  0,  then
       memkind_calloc() returns NULL.

       memkind_realloc()  changes the size of the previously allocated memory referenced by ptr to size bytes of
       the specified kind.  The contents of the memory remain unchanged up to the lesser  of  the  new  and  old
       sizes.  If  the  new  size  is  larger,  the  contents  of  the newly allocated portion of the memory are
       undefined. Upon success, the memory referenced by ptr is freed and  a  pointer  to  the  newly  allocated
       memory is returned.

       Note: memkind_realloc() may move the memory allocation, resulting in a different return value than ptr.

       If  ptr is NULL, the memkind_realloc() function behaves identically to memkind_malloc() for the specified
       size.  If size is equal to zero, and ptr is not NULL, then the call is equivalent  to  memkind_free(kind,
       ptr)  and  NULL  is returned. The address ptr, if not NULL, must have been returned by a previous call to
       memkind_malloc(),      memkind_calloc(),      memkind_realloc(),      memkind_defrag_reallocate()      or
       memkind_posix_memalign() with the same kind as specified to the call to memkind_realloc().  Otherwise, if
       memkind_free(kind, ptr) was called before, undefined behavior occurs.  In cases where the kind is unknown
       in  the  context  of  the  call  to  memkind_realloc()  NULL  can  be  given  as  the  kind  specified to
       memkind_realloc(), but this will require an internal look up for correct kind.  Note:  The  look  up  for
       kind  could result in serious performance penalty, which can be avoided by specifying a correct kind.  If
       kind is NULL and ptr is NULL, then memkind_realloc() returns NULL and sets errno to EINVAL.

       memkind_posix_memalign() allocates size bytes of memory of a specified kind such  that  the  allocation's
       base  address  is  an  even  multiple of alignment, and returns the allocation in the value pointed to by
       memptr.  The requested alignment must be a power of 2 at least as large as sizeof(void*).  If size is  0,
       then memkind_posix_memalign() returns 0, with a NULL returned in memptr.

       memkind_malloc_usable_size()  function provides the same semantics as malloc_usable_size(3), but operates
       on specified kind.
       Note: In cases where the kind is unknown in the context of the call to memkind_malloc_usable_size()  NULL
       can  be  given  as  the kind specified to memkind_malloc_usable_size(), but this could require a internal
       look up for correct kind.  memkind_malloc_usable_size() is supported by TBB  heap  manager  described  in
       ENVIRONMENT section since Intel TBB 2019 Update 4.

       memkind_defrag_reallocate()   reallocates   the  object  conditonally  inside  specific  kind.   Function
       determines if it's worthwhile to move allocation to reduce degree of external fragmentation of the  heap.
       In  case of failure function returns NULL, otherwise function returns a pointer to reallocated memory and
       memory  referenced  by  ptr  was  released  and  should  not  be  accessed.   If  ptr   is   NULL,   then
       memkind_defrag_reallocate()  returns NULL.  In cases where the kind is unknown in the context of the call
       to memkind_defrag_reallocate() NULL can be given as the kind  specified  to  memkind_defrag_reallocate(),
       but  this  will require an internal look up for correct kind.  Note: The look up for kind could result in
       serious performance penalty, which can be avoided by specifying a correct kind.

       memkind_detect_kind() returns the kind associated with allocated memory referenced by ptr.  This  pointer
       must  have  been  returned  by  a previous call to memkind_malloc(), memkind_calloc(), memkind_realloc(),
       memkind_defrag_reallocate() or memkind_posix_memalign().  If  ptr  is  NULL,  then  memkind_detect_kind()
       returns NULL.  Note: This function has non-trivial performance overhead.

       memkind_free() causes the allocated memory referenced by ptr to be made available for future allocations.
       This pointer  must  have  been  returned  by  a  previous  call  to  memkind_malloc(),  memkind_calloc(),
       memkind_realloc(),    memkind_defrag_reallocate()    or    memkind_posix_memalign().     Otherwise,    if
       memkind_free(kind, ptr) was already called before,  undefined  behavior  occurs.   If  ptr  is  NULL,  no
       operation  is performed.  In cases where the kind is unknown in the context of the call to memkind_free()
       NULL can be given as the kind specified to memkind_free(), but this will require an internal look up  for
       correct  kind.   Note:  The  look  up  for kind could result in serious performance penalty, which can be
       avoided by specifying a correct kind.

       KIND CONFIGURATION MANAGEMENT:
       The functions described in this section  define  a  way  to  create,  delete  and  update  kind  specific
       configuration.   Except  of  memkind_config_new(),  user  must specify the memkind configuration with the
       first argument to each function.  API described here is most useful with file-backed kind of memory, e.g.
       memkind_create_pmem_with_config() method.

       memkind_config_new() creates the memkind configuration.

       memkind_config_delete()  deletes  previously created memkind configuration, which must have been returned
       by a previous call to memkind_config_new().

       memkind_config_set_path() updates the memkind pmem_dir configuration parameter, which specifies directory
       path,  where  file-backed  kind  of  memory  will be created.  Note: This function does not validate that
       pmem_dir specifies a valid path.

       memkind_config_set_size() updates the memkind pmem_size configuration parameter, which  allows  to  limit
       the  file-backed kind memory partition.  Note: This function does not validate that pmem_size is in valid
       range.

       memkind_config_set_memory_usage_policy() updates the memkind policy configuration parameter, which allows
       to tune up memory utilization.  The user should set the value based on the characteristics of application
       that is using the library (e.g. prioritize memory usage, CPU utilization), for more details about  policy
       see the MEMORY USAGE POLICY section below.  Note: This function does not validate that policy is in valid
       range.

       KIND MANAGEMENT:
       There are built-in kinds that are always available and these are enumerated in  the  KINDS  section.  The
       user can also create their own kinds of memory. This section describes the API's that enable the tracking
       of the different kinds of memory and determining their properties.

       memkind_create_pmem() is a convenient function used to create a file-backed kind of memory.  It allocates
       a  temporary file in the given directory dir.  The file is created in a fashion similar to tmpfile(3), so
       that the file name does not appear when the directory is listed and the space is automatically freed when
       the  program  terminates.   The  file is truncated to a size of max_size bytes and the resulting space is
       memory-mapped.
       Note that  the  actual  file  system  space  is  not  allocated  immediately,  but  only  on  a  call  to
       memkind_pmem_mmap()  (see  memkind_pmem(3)).  This allows to create a pmem memkind of a pretty large size
       without the need to reserve in advance the corresponding file system space for the entire  heap.  If  the
       value of max_size equals 0, pmem memkind is only limited by the capacity of the file system mounted under
       dir argument.  The minimum max_size value which allows to limit the  size  of  kind  by  the  library  is
       defined  as  MEMKIND_PMEM_MIN_SIZE.   Calling  memkind_create_pmem()  with  a  size smaller than that and
       different than 0 will return an error.  The maximum allowed size is not limited by memkind,  but  by  the
       file system specified by the dir argument.  The max_size passed in is the raw size of the memory pool and
       jemalloc will use some of that space for its own metadata.  Returns zero if the pmem memkind  is  created
       successfully or an error code from the ERRORS section if not.

       memkind_create_pmem_with_config()  is  a  second  function  used  to create a file-backed kind of memory.
       Function behaves simillar to memkind_create_pmem() but instead of passing dir and max_size arguments,  it
       uses  config  param  to  specify  characteristics  of  created  file-backed  kind  of  memory  (see  KIND
       CONFIGURATION MANAGEMENT section).

       memkind_create_kind() creates kind that allocates memory with specific memory type, memory binding policy
       and  flags  (see  MEMORY  FLAGS  section).  The memtype_flags (see MEMORY TYPES section) determine memory
       types to allocate, policy argument is policy for specifying page binding  to  memory  types  selected  by
       memtype_flags.   Returns  zero  if  the  specified kind is created successfully or an error code from the
       ERRORS section if not.

       memkind_destroy_kind() destroys previously created kind object,  which  must  have  been  returned  by  a
       previous  call  to  memkind_create_pmem(),  memkind_create_pmem_with_config()  or  memkind_create_kind().
       Otherwise, or if memkind_destroy_kind(kind) was already called before, undefined behavior  occurs.   Note
       that,  when the kind was returned by memkind_create_kind() all allocated memory must be freed before kind
       is destroyed, otherwise this will cause memory leak. When the kind was returned by  memkind_create_pmem()
       or memkind_create_pmem_with_config() all allocated memory will be freed after kind will be destroyed.

       memkind_check_available()  returns  zero  if  the  specified  kind is available or an error code from the
       ERRORS section if it is not.

       MEMKIND_PMEM_MIN_SIZE The minimum size which allows to limit the file-backed memory partition.

       STATISTICS:
       The functions described in this section define a way to get specific memory allocation statistics.

       memkind_update_cached_stats() is used  to  force  an  update  of  cached  dynamic  allocator  statistics.
       Statistics are not updated real-time by memkind library and this method allows to force its update.

       memkind_get_stat()  retrieves  statistic of the specified type and returns it in value.  For more details
       about stat see the MEMORY STATISTICS TYPE section below.  Measured statistic applies  to  specific  kind,
       when NULL is given as kind then statistic applies to memory used by the whole memkind library.  Note: You
       need to call memkind_update_cached_stats()  before  calling  memkind_get_stat()  because  statistics  are
       cached by memkind library.

       DECORATORS:
       The  memkind  library  enables the user to define decorator functions that can be called before and after
       each memkind heap management API. The decorators that are called at the beginning of the function end are
       named  after  that  function  with  _pre appended to the name and those that are called at the end of the
       function are named after that function with _post appended to the name. These are  weak  symbols  and  if
       they  are not present at link time they are not called. The memkind library does not define these symbols
       which are reserved for user definition.  These decorators  can  be  used  to  track  calls  to  the  heap
       management  interface  or  to  modify  parameters. The decorators that are called at the beginning of the
       allocator pass all inputs by reference and the decorators that are called at the  end  of  the  allocator
       pass  the  output  by  reference.  This  enables  the  modification  of the input and output of each heap
       management function by the decorators.

       LIBRARY VERSION:
       The memkind library version scheme consist major, minor and patch numbers  separated  by  dot.  Combining
       those numbers, we got the following representation:
       major.minor.patch, where:
            -major number is incremented whenever API is changed (loss of backward compatibility),
            -minor  number  is  incremented  whenever  additional extensions are introduced or behavior has been
       changed,
            -patch number is incremented whenever small bug fixes are added.

       memkind library provide numeric representation of the version by exposing the following API:

       memkind_get_version() returns version number represented by a single integer number,  obtained  from  the
       formula:
       major * 1000000 + minor * 1000 + patch

       Note: major < 1 means unstable API.

       API standards:
       -STANDARD API, API is considered as stable
       -NON-STANDARD API, API is considered as stable, however this is not a standard way to use memkind
       -EXPERIMENTAL API, API is considered as unstable and the subject to change

RETURN VALUE

       memkind_calloc(), memkind_malloc(), memkind_realloc() and memkind_defrag_reallocate() returns the pointer
       to the allocated memory or NULL if the request fails.  memkind_malloc_usable_size() returns the number of
       usable bytes in the block of allocated memory pointed to by ptr, a pointer to a block of memory allocated
       by memkind_malloc() or  a  related  function.  If  ptr  is  NULL,  0  is  returned.   memkind_free()  and
       memkind_error_message()  do not have return values.  All other memkind API's return 0 upon success and an
       error code defined in the ERRORS  section  upon  failure.   The  memkind  library  avoids  setting  errno
       directly, but calls to underlying libraries and system calls may set errno (e.g.  memkind_create_pmem()).

KINDS

       The available kinds of memory:

       MEMKIND_DEFAULT
              Default allocation using standard memory and default page size.

       MEMKIND_HUGETLB
              Allocate from standard memory using huge pages.  Note: This kind requires huge pages configuration
              described in SYSTEM CONFIGURATION section.

       MEMKIND_GBTLB (DEPRECATED)
              Allocate from standard memory using 1GB chunks backed by huge pages.   Note:  This  kind  requires
              huge pages configuration described in SYSTEM CONFIGURATION section.

       MEMKIND_INTERLEAVE
              Allocate pages interleaved across all NUMA nodes with transparent huge pages disabled.

       MEMKIND_HBW
              Allocate  from  the closest high bandwidth memory NUMA node at the time of allocation. If there is
              not enough high bandwidth memory to satisfy the request errno is set to ENOMEM and  the  allocated
              pointer is set to NULL.

       MEMKIND_HBW_ALL
              Same  as  MEMKIND_HBW  except  decision regarding closest NUMA node is postponed until the time of
              first write.

       MEMKIND_HBW_HUGETLB
              Same as MEMKIND_HBW except the allocation is backed by huge pages.  Note: This kind requires  huge
              pages configuration described in SYSTEM CONFIGURATION section.

       MEMKIND_HBW_ALL_HUGETLB
              Combination  of MEMKIND_HBW_ALL and MEMKIND_HBW_HUGETLB properties.  Note: This kind requires huge
              pages configuration described in SYSTEM CONFIGURATION section.

       MEMKIND_HBW_PREFERRED
              Same as MEMKIND_HBW except that if there is not  enough  high  bandwidth  memory  to  satisfy  the
              request, the allocation will fall back on standard memory.

       MEMKIND_HBW_PREFERRED_HUGETLB
              Same  as  MEMKIND_HBW_PREFERRED  except  the  allocation is backed by huge pages.  Note: This kind
              requires huge pages configuration described in SYSTEM CONFIGURATION section.

       MEMKIND_HBW_GBTLB (DEPRECATED)
              Same as MEMKIND_HBW except the allocation is backed by 1GB chunks of huge pages.  Note  that  size
              can  take  on  any value, but full gigabyte pages will allocated for each request, so remainder of
              the last page will be wasted.  This kind requires huge pages  configuration  described  in  SYSTEM
              CONFIGURATION section.

       MEMKIND_HBW_PREFERRED_GBTLB (DEPRECATED)
              Same  as MEMKIND_HBW_GBTLB except that if there is not enough high bandwidth memory to satisfy the
              request, the allocation will fall back on standard memory.  Note: This kind  requires  huge  pages
              configuration described in SYSTEM CONFIGURATION section.

       MEMKIND_HBW_INTERLEAVE
              Same  as  MEMKIND_HBW except that the pages that support the allocation are interleaved across all
              high bandwidth nodes and transparent huge pages are disabled.

       MEMKIND_DAX_KMEM
              Allocate from the closest persistent memory NUMA node at the time of allocation. If there  is  not
              enough  memory  in  the closest persistent memory NUMA node to satisfy the request errno is set to
              ENOMEM and the allocated pointer is set to NULL.

       MEMKIND_DAX_KMEM_ALL
              Allocate from the closest persistent memory NUMA node available at  the  time  of  allocation.  If
              there  is not enough memory on any of persistent memory NUMA nodes to satisfy the request errno is
              set to ENOMEM and the allocated pointer is set to NULL.

       MEMKIND_DAX_KMEM_PREFERRED
              Same as MEMKIND_DAX_KMEM except that if there is not  enough  memory  in  the  closest  persistent
              memory NUMA node to satisfy the request, the allocation will fall back on other memory NUMA nodes.
              Note: For this kind, the allocation will not succeed if two or more persistent memory  NUMA  nodes
              are  in  the same shortest distance to the same CPU on which process is eligible to run.  Check on
              that eligibility is done upon starting the application.

       MEMKIND_REGULAR
              Allocate from regular memory using the default page size. Regular  means  general  purpose  memory
              from the NUMA nodes containing CPUs.

MEMORY TYPES

       The available types of memory:

       MEMKIND_MEMTYPE_DEFAULT
              Standard memory, the same as process uses.

       MEMKIND_MEMTYPE_HIGH_BANDWIDTH
              High  bandwidth  memory (HBM). There must be at least two memory types with different bandwidth to
              determine which is the HBM.

MEMORY BINDING POLICY

       The available types of memory binding policy:

       MEMKIND_POLICY_BIND_LOCAL
              Allocate local memory. If there is not enough memory to satisfy the request errno is set to ENOMEM
              and the allocated pointer is set to NULL.

       MEMKIND_POLICY_BIND_ALL
              Memory  locality  is ignored. If there is not enough memory to satisfy the request errno is set to
              ENOMEM and the allocated pointer is set to NULL.

       MEMKIND_POLICY_PREFERRED_LOCAL
              Allocate preferred memory that is local.  If there is not enough preferred memory to  satisfy  the
              request or preferred memory is not available, the allocation will fall back on any other memory.

       MEMKIND_POLICY_INTERLEAVE_LOCAL
              Interleave  allocation across local memory.  For n memory types the allocation will be interleaved
              across all of them.

       MEMKIND_POLICY_INTERLEAVE_ALL
              Interleave allocation. Locality is ignored.  For n memory types the allocation will be interleaved
              across all of them.

       MEMKIND_POLICY_MAX_VALUE
              Max policy value.

MEMORY FLAGS

       The available types of memory flags:

       MEMKIND_MASK_PAGE_SIZE_2MB
              Allocation backed by 2MB page size.

MEMORY USAGE POLICY

       The available types of memory usage policy:

       MEMKIND_MEM_USAGE_POLICY_DEFAULT
              Default memory usage policy.

       MEMKIND_MEM_USAGE_POLICY_CONSERVATIVE
              Conservative  memory  usage policy - prioritize memory usage at cost of performance.  Note: Memory
              usage policies have no effect for TBB heap manager described in ENVIRONMENT section.

MEMORY STATISTICS TYPE

       The available types of memory statistics:

       MEMKIND_STAT_TYPE_RESIDENT
              Maximum number of bytes in physically resident data pages mapped.

       MEMKIND_STAT_TYPE_ACTIVE
              Total number of bytes in active pages.

       MEMKIND_STAT_TYPE_ALLOCATED
              Total number of allocated bytes.

ERRORS

       memkind_posix_memalign()
              returns the one of the POSIX standard error codes EINVAL or ENOMEM as defined in <errno.h>  if  an
              error occurs (these have positive values).  If the alignment parameter is not a power of two or is
              not a multiple of sizeof(void*), then EINVAL is returned.  If  there  is  insufficient  memory  to
              satisfy the request then ENOMEM is returned.

       All  functions  other  than  memkind_posix_memalign() which have an integer return type return one of the
       negative error codes as defined in <memkind.h> and described below.

       MEMKIND_ERROR_UNAVAILABLE
              Requested memory kind is not available

       MEMKIND_ERROR_MBIND
              Call to mbind(2) failed

       MEMKIND_ERROR_MMAP
              Call to mmap(2) failed

       MEMKIND_ERROR_MALLOC
              Call to jemalloc's malloc() failed

       MEMKIND_ERROR_ENVIRON
              Error parsing environment variable MEMKIND_*

       MEMKIND_ERROR_INVALID
              Invalid input arguments to memkind routine

       MEMKIND_ERROR_TOOMANY
              Error trying to initialize more than maximum MEMKIND_MAX_KIND number of kinds

       MEMKIND_ERROR_BADOPS
              Error memkind operation structure is missing or invalid

       MEMKIND_ERROR_HUGETLB
              Unable to allocate huge pages

       MEMKIND_ERROR_MEMTYPE_NOT_AVAILABLE
              Error requested memory type is not available

       MEMKIND_ERROR_OPERATION_FAILED
              Error memkind operation failed

       MEMKIND_ERROR_ARENAS_CREATE
              Call to jemalloc's arenas.create() failed

       MEMKIND_ERROR_RUNTIME
              Unspecified run-time error

FILES

       /usr/bin/memkind-hbw-nodes
              Prints a comma-separated list of high bandwidth nodes.

       /usr/bin/memkind-auto-dax-kmem-nodes
              Prints a comma-separated list of persistent memory NUMA nodes, which are automatically detected.

ENVIRONMENT

       MEMKIND_HBW_NODES
              This environment variable is a comma-separated list  of  NUMA  nodes  that  are  treated  as  high
              bandwidth.  Uses  the libnuma routine numa_parse_nodestring() for parsing, so the syntax described
              in the numa(3) man page for this routine applies: e.g. 1-3,5 is a valid setting.

       MEMKIND_DAX_KMEM_NODES
              This environment variable is a comma-separated list of NUMA nodes that are treated as PMEM memory.
              Uses  the  libnuma  routine  numa_parse_nodestring()  for  parsing, so the syntax described in the
              numa(3) man page for this routine applies: e.g. 1-3,5 is a valid setting.

       MEMKIND_ARENA_NUM_PER_KIND
              This environment variable allows leveraging internal mechanism of the library for  setting  number
              of  arenas  per  kind.  Value  should  be  a positive integer (not greater than INT_MAX defined in
              <limits.h>).  The user should set the value based on the characteristics of  application  that  is
              using  the  library.  Higher  value  can  provide  better  performance  in extremely multithreaded
              applications at the cost of memory overhead. See section IMPLEMENTATION NOTES of  jemalloc(3)  for
              more details about arenas.

       MEMKIND_HOG_MEMORY
              Controls  behavior  of  memkind  with  regards  to  returning  memory  to  underlying  OS. Setting
              MEMKIND_HOG_MEMORY to 1 causes memkind to not release memory to OS in anticipation of memory reuse
              soon. This will improve latency of 'free' operations but increase memory usage.

       MEMKIND_DEBUG
              Controls  logging  mechanism in memkind. Setting MEMKIND_DEBUG to 1 enables printing messages like
              errors and general information about environment to stderr.

       MEMKIND_BACKGROUND_THREAD_LIMIT
              Enable background worker threads.  Value should be  from  range  0  to  maximum  number  of  cpus.
              Setting  MEMKIND_BACKGROUND_THREAD_LIMIT to specific value will limit maximum number of background
              worker threads to this value.  0 means maximum number of background worker threads will be limited
              to maximum number of cpus.

       MEMKIND_HEAP_MANAGER
              Controls  heap  management  behavior  in memkind library by switching to one of the available heap
              managers.
              Values:
                  JEMALLOC - sets the jemalloc heap manager
                  TBB - sets the Intel Threading Building Blocks heap manager. This option requires installed
                  Intel Threading Building Blocks library.

       If the MEMKIND_HEAP_MANAGER is not set then the jemalloc heap manager will be used by default.

SYSTEM CONFIGURATION

       Interfaces for obtaining 2MB (HUGETLB) memory need allocated huge pages in the kernel's huge page pool.

       HUGETLB (huge pages)
              Current number of "persistent"  huge  pages  can  be  read  from  /proc/sys/vm/nr_hugepages  file.
              Proposed  way  of  setting  hugepages is: sudo sysctl vm.nr_hugepages=<number_of_hugepages>.  More
              information can be found here: ⟨https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt⟩

STATIC LINKING

       When linking statically against memkind, libmemkind.a should  be  used  together  with  its  dependencies
       libnuma  and pthread. Pthread can be linked by adding /usr/lib64/libpthread.a as a dependency (exact path
       may vary). Typically libnuma will need to be compiled from sources to use  it  as  a  static  dependency.
       libnuma can be reached on GitHub: ⟨https://github.com/numactl/numactl⟩

KNOWN ISSUES

       HUGETLB (huge pages)
              There  might  be  some  overhead  in  huge  pages  consumption caused by heap management.  If your
              allocation fails because of OOM, please try to allocate extra huge pages (e.g. 8 huge pages).

       Copyright (C) 2014 - 2019 Intel Corporation. All rights reserved.

SEE ALSO

       malloc(3), malloc_usable_size(3), numa(3), numactl(8),  mbind(2),  mmap(2),  move_pages(2),  jemalloc(3),
       memkind_dax_kmem(3),    memkind_default(3),    memkind_arena(3),    memkind_hbw(3),   memkind_hugetlb(3),
       memkind_pmem(3)