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.\" Automatically generated by Pandoc 2.1.3
.\"
.TH "PMEM_MEMMOVE_PERSIST" "3" "2018-07-18" "PMDK - pmem API version 1.1" "PMDK Programmer's Manual"
.hy
.\" Copyright 2014-2018, Intel Corporation
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" * Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" * Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" * Neither the name of the copyright holder nor the names of its
.\" contributors may be used to endorse or promote products derived
.\" from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
.\" OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
.\" OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.SH NAME
.PP
\f[B]pmem_memmove\f[](), \f[B]pmem_memcpy\f[](), \f[B]pmem_memset\f[](),
\f[B]pmem_memmove_persist\f[](), \f[B]pmem_memcpy_persist\f[](),
\f[B]pmem_memset_persist\f[](), \f[B]pmem_memmove_nodrain\f[](),
\f[B]pmem_memcpy_nodrain\f[](), \f[B]pmem_memset_nodrain\f[]() \-
functions that provide optimized copying to persistent memory
.SH SYNOPSIS
.IP
.nf
\f[C]
#include\ <libpmem.h>
void\ *pmem_memmove(void\ *pmemdest,\ const\ void\ *src,\ size_t\ len,\ unsigned\ flags);
void\ *pmem_memcpy(void\ *pmemdest,\ const\ void\ *src,\ size_t\ len,\ unsigned\ flags);
void\ *pmem_memset(void\ *pmemdest,\ int\ c,\ size_t\ len,\ unsigned\ flags);
void\ *pmem_memmove_persist(void\ *pmemdest,\ const\ void\ *src,\ size_t\ len);
void\ *pmem_memcpy_persist(void\ *pmemdest,\ const\ void\ *src,\ size_t\ len);
void\ *pmem_memset_persist(void\ *pmemdest,\ int\ c,\ size_t\ len);
void\ *pmem_memmove_nodrain(void\ *pmemdest,\ const\ void\ *src,\ size_t\ len);
void\ *pmem_memcpy_nodrain(void\ *pmemdest,\ const\ void\ *src,\ size_t\ len);
void\ *pmem_memset_nodrain(void\ *pmemdest,\ int\ c,\ size_t\ len);
\f[]
.fi
.SH DESCRIPTION
.PP
\f[B]pmem_memmove\f[](), \f[B]pmem_memcpy\f[]() and
\f[B]pmem_memset\f[]() functions provide the same memory copying as
their namesakes \f[B]memmove\f[](3), \f[B]memcpy\f[](3) and
\f[B]memset\f[](3), and ensure that the result has been flushed to
persistence before returning (unless \f[B]PMEM_F_MEM_NOFLUSH\f[] flag
was used).
.PP
For example, the following code is functionally equivalent to
\f[B]pmem_memmove\f[]() (with flags equal to 0):
.IP
.nf
\f[C]
\ \ \ \ memmove(dest,\ src,\ len);
\ \ \ \ pmem_persist(dest,\ len);
\f[]
.fi
.PP
Calling \f[B]pmem_memmove\f[]() may out\-perform the above code, because
\f[B]libpmem\f[](7) implementation may take advantage of the fact that
\f[I]pmemdest\f[] is persistent memory and use instructions such as
\f[I]non\-temporal\f[] stores to avoid the need to flush processor
caches.
.RS
.PP
WARNING: Using these functions where \f[B]pmem_is_pmem\f[](3) returns
false may not do anything useful.
Use libc functions in that case.
.RE
.PP
Unlike libc implementation, \f[B]libpmem\f[] functions guarantee that if
destination buffer address and length are 8 byte aligned then all stores
will be performed using at least 8 byte store instructions.
This means that a series of 8 byte stores followed by
\f[B]pmem_persist\f[](3) can be safely replaced by a single call to one
of the above functions.
.PP
The \f[I]flags\f[] argument of all of the above functions has the same
meaning.
It can be 0 or a bitwise OR of one or more of the following flags:
.IP \[bu] 2
\f[B]PMEM_F_MEM_NODRAIN\f[] \- modifies the behavior to skip the final
\f[B]pmem_drain\f[]() step.
This allows applications to optimize cases where several ranges are
being copied to persistent memory, followed by a single call to
\f[B]pmem_drain\f[]().
The following example illustrates how this flag might be used to avoid
multiple calls to \f[B]pmem_drain\f[]() when copying several ranges of
memory to pmem:
.IP
.nf
\f[C]
/*\ ...\ write\ several\ ranges\ to\ pmem\ ...\ */
pmem_memcpy(pmemdest1,\ src1,\ len1,\ PMEM_F_MEM_NODRAIN);
pmem_memcpy(pmemdest2,\ src2,\ len2,\ PMEM_F_MEM_NODRAIN);
/*\ ...\ */
/*\ wait\ for\ any\ pmem\ stores\ to\ drain\ from\ HW\ buffers\ */
pmem_drain();
\f[]
.fi
.IP \[bu] 2
\f[B]PMEM_F_MEM_NOFLUSH\f[] \- Don't flush anything.
This implies \f[B]PMEM_F_MEM_NODRAIN\f[].
Using this flag only makes sense when it's followed by any function that
flushes data.
.PP
The remaining flags say \f[I]how\f[] the operation should be done, and
are merely hints.
.IP \[bu] 2
\f[B]PMEM_F_MEM_NONTEMPORAL\f[] \- Use non\-temporal instructions.
This flag is mutually exclusive with \f[B]PMEM_F_MEM_TEMPORAL\f[].
On x86_64 this flag is mutually exclusive with
\f[B]PMEM_F_MEM_NOFLUSH\f[].
.IP \[bu] 2
\f[B]PMEM_F_MEM_TEMPORAL\f[] \- Use temporal instructions.
This flag is mutually exclusive with \f[B]PMEM_F_MEM_NONTEMPORAL\f[].
.IP \[bu] 2
\f[B]PMEM_F_MEM_WC\f[] \- Use write combining mode.
This flag is mutually exclusive with \f[B]PMEM_F_MEM_WB\f[].
On x86_64 this is an alias for \f[B]PMEM_F_MEM_NONTEMPORAL\f[].
On x86_64 this flag is mutually exclusive with
\f[B]PMEM_F_MEM_NOFLUSH\f[].
.IP \[bu] 2
\f[B]PMEM_F_MEM_WB\f[] \- Use write back mode.
This flag is mutually exclusive with \f[B]PMEM_F_MEM_WC\f[].
On x86_64 this is an alias for \f[B]PMEM_F_MEM_TEMPORAL\f[].
.PP
Using an invalid combination of flags has undefined behavior.
.PP
Without any of the above flags \f[B]libpmem\f[] will try to guess the
best strategy based on size.
See \f[B]PMEM_MOVNT_THRESHOLD\f[] description in \f[B]libpmem\f[](7) for
details.
.PP
\f[B]pmem_memmove_persist\f[]() is an alias for \f[B]pmem_memmove\f[]()
with flags equal to 0.
.PP
\f[B]pmem_memcpy_persist\f[]() is an alias for \f[B]pmem_memcpy\f[]()
with flags equal to 0.
.PP
\f[B]pmem_memset_persist\f[]() is an alias for \f[B]pmem_memset\f[]()
with flags equal to 0.
.PP
\f[B]pmem_memmove_nodrain\f[]() is an alias for \f[B]pmem_memmove\f[]()
with flags equal to \f[B]PMEM_F_MEM_NODRAIN\f[].
.PP
\f[B]pmem_memcpy_nodrain\f[]() is an alias for \f[B]pmem_memcpy\f[]()
with flags equal to \f[B]PMEM_F_MEM_NODRAIN\f[].
.PP
\f[B]pmem_memset_nodrain\f[]() is an alias for \f[B]pmem_memset\f[]()
with flags equal to \f[B]PMEM_F_MEM_NODRAIN\f[].
.SH RETURN VALUE
.PP
All of the above functions return address of the destination buffer.
.SH CAVEATS
.PP
After calling any of the functions with \f[B]PMEM_F_MEM_NODRAIN\f[] flag
you should not expect memory to be visible to other threads before
calling \f[B]pmem_drain\f[](3) or any of the \f[I]_persist\f[]
functions.
This is because on x86_64 those functions may use non\-temporal store
instructions, which are weakly ordered.
See \[lq]Intel 64 and IA\-32 Architectures Software Developer's
Manual\[rq], Volume 1, \[lq]Caching of Temporal vs.\ Non\-Temporal
Data\[rq] section for details.
.SH SEE ALSO
.PP
\f[B]memcpy\f[](3), \f[B]memmove\f[](3), \f[B]memset\f[](3),
\f[B]libpmem\f[](7) and \f[B]<http://pmem.io>\f[]
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