92
Managing Memory Pools and Poolsets
The pmempool utility has several features that developers and system administrators
may find useful. We do not present their details here because each command has a
detailed man page:
• pmempool info prints information and statistics in human-readable
format about the specified pool.
• pmempool check checks the pool’s consistency and repairs pool if it
is not consistent.
• pmempool create creates a pool of specified type with additional
properties specific for this type of pool.
• pmempool dump dumps usable data from a pool in hexadecimal or
binary format.
• pmempool rm removes pool file or all pool files listed in pool set
configuration file.
• pmempool convert updates the pool to the latest available layout
version.
• pmempool sync synchronizes replicas within a poolset.
• pmempool transform modifies the internal structure of a poolset.
• pmempool feature toggles or queries a poolset’s features.
Typed Object Identifiers (TOIDs)
When we write data to a persistent memory pool or device, we commit it at a physical
address. With the ASLR feature of operating systems, when applications open a pool and
memory map it into the address space, the virtual address will change each time. For this
reason, a type of handle (pointer) that does not change is needed; this handle is called
an OID (object identifier). Internally, it is a pair of the pool or poolset unique identifier
(UUID) and an offset within the pool or poolset. The OID can be translated back and
forth between its persistent form and pointers that are fit for direct use by this particular
instance of your program.
Chapter 7 libpmemobj: a Native traNsaCtioNal objeCt store
Managing Memory Pools and Poolsets
The pmempool utility has several features that developers and system administrators
may find useful. We do not present their details here because each command has a
detailed man page:
• pmempool info prints information and statistics in human-readable
format about the specified pool.
• pmempool check checks the pool’s consistency and repairs pool if it
is not consistent.
• pmempool create creates a pool of specified type with additional
properties specific for this type of pool.
• pmempool dump dumps usable data from a pool in hexadecimal or
binary format.
• pmempool rm removes pool file or all pool files listed in pool set
configuration file.
• pmempool convert updates the pool to the latest available layout
version.
• pmempool sync synchronizes replicas within a poolset.
• pmempool transform modifies the internal structure of a poolset.
• pmempool feature toggles or queries a poolset’s features.
Typed Object Identifiers (TOIDs)
When we write data to a persistent memory pool or device, we commit it at a physical
address. With the ASLR feature of operating systems, when applications open a pool and
memory map it into the address space, the virtual address will change each time. For this
reason, a type of handle (pointer) that does not change is needed; this handle is called
an OID (object identifier). Internally, it is a pair of the pool or poolset unique identifier
(UUID) and an offset within the pool or poolset. The OID can be translated back and
forth between its persistent form and pointers that are fit for direct use by this particular
instance of your program.
Chapter 7 libpmemobj: a Native traNsaCtioNal objeCt store