106 строки
3.7 KiB
Plaintext
106 строки
3.7 KiB
Plaintext
.\" -*- nroff -*-
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.\" Copyright (c) 2015 University of Houston. All rights reserved.
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.\" Copyright (c) 2015 Mellanox Technologies, Inc.
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.\" $COPYRIGHT$
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.de Vb
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.ft CW
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.nf
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..
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.de Ve
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.ft R
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.fi
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..
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.TH "SHMALLOC" "3" "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fIshmalloc\fP(3),
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\fIshfree\fP(3),
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\fIshmemalign\fP(3),
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\fIshrealloc\fP(3)
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\- Symmetric heap memory management functions.
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.SH SYNOPSIS
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C or C++:
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.Vb
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#include <mpp/shmem.h>
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void *shmalloc(size_t size);
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void shfree(void *ptr);
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void *shrealloc(void *ptr, size_t size);
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void *shmemalign(size_t alignment, size_t size);
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extern long malloc_error;
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.Ve
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.SH DESCRIPTION
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The \fBshmalloc\fP
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function returns a pointer to a block of at least size bytes
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suitably aligned for any use. This space is allocated from the symmetric heap (in contrast
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to \fImalloc\fP(3C),
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which allocates from the private heap).
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.PP
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The \fBshmemalign\fP
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function allocates a block in the symmetric heap that has a
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byte alignment specified by the alignment argument.
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.PP
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The \fBshfree\fP
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function causes the block to which ptr points to, to be deallocated,
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that is, made available for further allocation. If ptr is a null pointer, no action
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occurs; otherwise, if the argument does not match a pointer earlier returned by a symmetric
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heap function, or if the space has already been deallocated, malloc_error is set to indicate the
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error, and shfree returns.
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.PP
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The \fBshrealloc\fP
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function changes the size of the block to which ptr points to, to the
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size (in bytes) specified by size.
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.PP
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The contents of the block are unchanged up to the lesser of the new and old sizes. If the new
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size is larger, the value of the newly allocated portion of the block is indeterminate. If ptr is a
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null pointer, the shrealloc function behaves like the shmalloc function for the specified size. If
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size is 0 and ptr is not a null pointer, the block to which it points to is freed. Otherwise, if ptr
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does not match a pointer earlier returned by a symmetric heap function, or if the space has
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already been deallocated, the malloc_error variable is set to indicate the error, and shrealloc
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returns a null pointer. If the space cannot be allocated, the block to which ptr points to is
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unchanged.
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.PP
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The shmalloc, shfree, and shrealloc functions are provided so that multiple PEs in an
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application can allocate symmetric, remotely accessible memory blocks. These memory
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blocks can then be used with (shmem) communication routines. Each of these functions call
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the \fIshmem_barrier_all\fP(3)
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function before returning; this ensures that all PEs
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participate in the memory allocation, and that the memory on other PEs can be used as soon
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as the local PE returns.
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.PP
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The user is responsible for calling these functions with identical argument(s) on all PEs; if
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differing size arguments are used, subsequent calls may not return the same symmetric heap
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address on all PEs.
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.PP
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.SH NOTES
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The total size of the symmetric heap is determined at job startup. One can adjust the size of
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the heap using the SHMEM_SYMMETRIC_HEAP_SIZE environment variable. See the
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\fIintro_shmem\fP(3)
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man page for futher details.
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The shmalloc, shfree, and shrealloc functions differ from the private heap allocation functions
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in that all PEs in an application must call them (a barrier is used to ensure this).
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.PP
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.SH RETURN VALUES
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The \fBshmalloc\fP
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function returns a pointer to the allocated space (which should
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be identical on all PEs); otherwise, it returns a null pointer (with malloc_error set).
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The \fBshfree\fP
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function returns no value.
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The \fBshrealloc\fP
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function returns a pointer to the allocated space (which
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may have moved); otherwise, it returns a null pointer (with malloc_error set).
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.SH SEE ALSO
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\fIintro_shmem\fP(3),
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\fImy_pe\fP(3I),
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\fIstart_pes\fP(3)
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