NAME

       pmemblk_ctl_get(),  pmemblk_ctl_set(),  pmemblk_ctl_exec()  -  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>