NAME

       pmemblk_ctl_get()(DEPRECATED),                              pmemblk_ctl_set()(DEPRECATED),
       pmemblk_ctl_exec()(DEPRECATED)  -  Query   and   modify   libpmemblk   internal   behavior
       (EXPERIMENTAL)

SYNOPSIS

              #include <libpmemblk.h>

              int pmemblk_ctl_get(PMEMblkpool *pbp, const char *name, void *arg); (EXPERIMENTAL)
              int pmemblk_ctl_set(PMEMblkpool *pbp, const char *name, void *arg); (EXPERIMENTAL)
              int pmemblk_ctl_exec(PMEMblkpool *pbp, const char *name, void *arg); (EXPERIMENTAL)

DESCRIPTION

       The  pmemblk_ctl_get(),  pmemblk_ctl_set()  and  pmemblk_ctl_exec()  functions  provide  a
       uniform interface for querying  and  modifying  the  internal  behavior  of  libpmemblk(7)
       through the control (CTL) namespace.

       The  name argument specifies an entry point as defined in the CTL namespace specification.
       The entry point description specifies whether  the  extra  arg  is  required.   Those  two
       parameters  together  create  a CTL query.  The functions and the entry points are thread-
       safe unless indicated otherwise below.  If there are special  conditions  for  calling  an
       entry  point,  they are explicitly stated in its description.  The functions propagate the
       return value of the entry point.  If either name or arg is invalid, -1 is returned.

       If the provided ctl query is valid, the CTL functions will always return 0 on success  and
       -1 on failure, unless otherwise specified in the entry point description.

       See more in pmem_ctl(5) man page.

CTL NAMESPACE

       prefault.at_create | rw | global | int | int | - | boolean

       If set, every page of the pool will be touched and written to when the pool is created, in
       order to trigger page allocation  and  minimize  the  performance  impact  of  pagefaults.
       Affects only the pmemblk_create() function.

       Always returns 0.

       prefault.at_open | rw | global | int | int | - | boolean

       If  set, every page of the pool will be touched and written to when the pool is opened, in
       order to trigger page allocation  and  minimize  the  performance  impact  of  pagefaults.
       Affects only the pmemblk_open() function.

       Always returns 0.

       sds.at_create | rw | global | int | int | - | boolean

       If  set,  force-enables  or force-disables SDS feature during pool creation.  Affects only
       the pmemblk_create() function.  See pmempool_feature_query(3) for  information  about  SDS
       (SHUTDOWN_STATE) feature.

       Always returns 0.

       copy_on_write.at_open | rw | global | int | int | - | boolean

       If set, pool is mapped in such a way that modifications don’t reach the underlying medium.
       From the user’s perspective this means that when  the  pool  is  closed  all  changes  are
       reverted.  This feature is not supported for pools located on Device DAX.

       Always returns 0.

CTL EXTERNAL CONFIGURATION

       In  addition  to  direct  function  call, each write entry point can also be set using two
       alternative methods.

       The first method is to load a configuration directly  from  the  PMEMBLK_CONF  environment
       variable.

       The  second  method  of  loading an external configuration is to set the PMEMBLK_CONF_FILE
       environment variable to point to a file that contains a sequence of ctl queries.

       See more in pmem_ctl(5) man page.

SEE ALSO

       libpmemblk(7), pmem_ctl(5) and <https://pmem.io>