librpmem

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The librpmem library

Note: The alternative solution for accessing remote persistent memory is implemented by librpma. Note: This is a deprecated API and should not be used in production environments.

librpmem provides low-level support for remote access to persistent memory (pmem) utilizing RDMA-capable RNICs. The library can be used to replicate remotely a memory region over RDMA protocol. It utilizes appropriate persistency mechanism based on remote node’s platform capabilities. The librpmem utilizes the ssh client to authenticate a user on remote node and for encryption of connection’s out-of-band configuration data. See SSH section for details.

This library is for applications that use remote persistent memory directly, without the help of any library-supplied transactions or memory allocation. Higher-level libraries that build on libpmem are available and are recommended for most applications, see:

Man pages that contains a list of the Linux interfaces provided:

The rpmemd utility

Note: This is a deprecated utility and should not be used in production environments.

The rpmemd process is executed on target node by librpmem library over ssh(1) and facilitates access to persistent memory over RDMA.

See the rpmemd man page documentation and examples for the latest stable release or browse older versions there.

librpmem Examples

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#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <librpmem.h>

#define POOL_SIZE	(32 * 1024 * 1024)
#define NLANES		4

int
main(int argc, char *argv[])
{
	int ret;
	unsigned nlanes = NLANES;

	/* allocate a page size aligned local memory pool */
	long pagesize = sysconf(_SC_PAGESIZE);
	void *pool;
	ret = posix_memalign(&pool, pagesize, POOL_SIZE);
	if (ret) {
		fprintf(stderr, "posix_memaling: %s\n", strerror(ret));
		return 1;
	}
	assert(pool != NULL);

	/* fill pool_attributes */
	struct rpmem_pool_attr pool_attr;
	memset(&pool_attr, 0, sizeof(pool_attr));

	/* create a remote pool */
	RPMEMpool *rpp = rpmem_create("localhost", "pool.set",
		pool, POOL_SIZE, &nlanes, &pool_attr);
	if (!rpp) {
		fprintf(stderr, "rpmem_create: %s\n", rpmem_errormsg());
		return 1;
	}

	/* store data in the local pool */
	memset(pool, 0, POOL_SIZE);

	/* make local data persistent on the target node */
	ret = rpmem_persist(rpp, 0, POOL_SIZE, 0);
	if (ret) {
		fprintf(stderr, "rpmem_persist: %s\n", rpmem_errormsg());
		return 1;
	}

	/* close the remote pool */
	ret = rpmem_close(rpp);
	if (ret) {
		fprintf(stderr, "rpmem_close: %s\n", rpmem_errormsg());
		return 1;
	}

	/* release the local memory pool */
	free(pool);

	return 0;
}

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