本文主要是介绍RDMA编程实例rdma_cm API,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
RDMA编程基础
存储大师班 | RDMA简介与编程基础 -https://zhuanlan.zhihu.com/p/387549948
1. RDMA的学习环境搭建
RDMA需要专门的RDMA网卡或者InfiniBand卡才能使用,学习RDMA而又没有这些硬件设备,可以使用一个软件RDMA模拟环境,softiwarp ,
- 这是加载地址:https://github.com/zrlio/softiwarp
- 这是安装教程:http://www.reflectionsofthevoid.com/2011/03/how-to-install-soft-iwarp-on-ubuntu.html
更多的rdmacm实例:,
- https://github.com/tarickb/the-geek-in-the-corner
需要注意的是,这个例子里面缺省用的是IPv6连接,如果希望在IPv4环境下测试,需要先改代码用IPv4地址。
2. RDMA与socket的类比
和Socket连接类似,RDMA连接也分为可靠连接和不可靠连接。然而也不完全相同,Socket的可靠连接就是TCP连接,是流式的;不可靠连接也就是UDP,是消息式的。对于RDMA来说,无论是可靠连接和不可靠连接,都是消息式的。
编程角度看,RDMA代码也分为Server端,Client端,也有bind, listen, connect, accept,等动作,然而细节上仍有不少区别。
大家可以关注一下mellonx的vma,貌似可以直接用socket api通信,方便很多:
【RDMA】降低CPU除了RDMA (vbers)还是VMA ?|使用socket进行RDMA编程?_bandaoyu的note-CSDN博客
前言看介绍,像是mellonx针对其kernel bypass网卡(RDMA网卡)提供的一个lib库,该lib库对外提供socket api,使得用户的程序不需要修改就可以直接使用kernel bypass网卡(如RDMA网卡)。我们都知道RDMA 网卡目前使用的是rdma_cm和vbers api编程,和socket不一样,如果能用socket对RDMA编程,那确实是很大的利好。官网介绍什么是VMA?Mellanox Interconnect Community官方介绍:M
https://blog.csdn.net/bandaoyu/article/details/120726746
rdma_cm API说明:
https://linux.die.net/man/3/rdma_create_id (推荐)
https://www.ibm.com/docs/en/aix/7.2?topic=operations-rdma-listen (内容少)
rdma_cm API 管理连接(建立连接和销毁)+vbers api 管理收发
RDMA主机使用queue pairs(QP)进行通信;主机创建由发送队列SQ和接收队列RQ组成的QP,并使用verbs API将操作post 到这些队列。(所以rdma_cm是管理连接的,收发还是verbs API。)
3. RDMA服务器的代码流程
main()
{
channel=rdma_create_event_channel
这一步是创建一个event channel,event channel是RDMA设备在操作完成后,或者有连接请求等事件发生时,用来通知应用程序的通道。其内部就是一个file descriptor, 因此可以进行poll等操作。
rdma_create_id(channel, **id,……)
这一步创建一个rdma_cm_id, 概念上等价与socket编程时的listen socket。
rdma_bind_addr(id,addr)
和socket编程一样,也要先绑定一个本地的地址和端口,以进行listen操作。
rdma_listen(id,block)
开始侦听客户端的连接请求
rdma_get_cm_event(channel,&event)
这个调用就是作用在第一步创建的event channel上面,要从event channel中获取一个事件。这是个阻塞调用,只有有事件时才会返回。在一切正常的情况下,函数返回时会得到一个 RDMA_CM_EVENT_CONNECT_REQUEST事件,也就是说,有客户端发起连接了。
在事件的参数里面,会有一个新的rdma_cm_id传入。这点和socket是不同的,socket只有在accept后才有新的socket fd创建。
on_event()
{
on_connect_request()//RDMA_CM_EVENT_CONNECT_REQUEST
{
build_context()
{
6.ibv_alloc_pd
创建一个protection domain。protection domain可以看作是一个内存保护单位,在内存区域和队列直接建立一个关联关系,防止未授权的访问。
7.ibv_create_comp_channel
和之前创建的event channel类似,这也是一个event channel,但只用来报告【完成队列】里面的事件。当【完成队列】里有新的任务完成时,就通过这个channel向应用程序报告。
8.ibv_create_cq
创建【完成队列】,创建时就指定使用第6步的channel。
}//--end build_context()
9.rdma_create_qp
创建一个queue pair, 一个queue pair包括一个发送queue和一个接收queue. 指定使用前面创建的cq作为完成队列。该qp创建时就指定关联到第6步创建的pd上。
10.ibv_reg_mr
注册内存区域。RDMA使用的内存,必须事先进行注册。这个是可以理解的,DMA的内存在边界对齐,能否被swap等方面,都有要求。
11.rdma_accept
至此,做好了全部的准备工作,可以调用accept接受客户端的这个请求了。 –:)长出一口气 ~~ 且慢,
}
//--end on_connect_request()
12.rdma_ack_cm_event
对于每个从event channel得到的事件,都要调用ack函数,否则会产生内存泄漏。这一步的ack是对应第5步的get。每一次get调用,都要有对应的ack调用。
13.rdma_get_cm_event
继续调用rdma_get_cm_event, 一切正常的话我们此时应该得到 RDMA_CM_EVENT_ESTABLISHED 事件,表示连接已经建立起来。不需要做额外的处理,直接rdma_ack_cm_event就行了
}//--end on_event()
终于可以开始进行数据传输了 ==== (如何传输下篇再说)
参考:http://10.165.104.246:8080/#/c/43882/
4. 关闭连接
断开连接
当rdma_get_cm_event返回RDMA_CM_EVENT_DISCONNECTED事件时,表示客户端断开了连接,server端要进行对应的清理。此时可以调用rdma_ack_cm_event释放事件资源。然后依次调用下面的函数,释放连接资源,内存资源,队列资源。
rdma_disconnect
rdma_destroy_qp
ibv_dereg_mr
rdma_destroy_id
释放同客户端连接的rdma_cm_id
rdma_destroy_id
释放用于侦听的rdma_cm_id
rdma_destroy_event_channel
释放 event channel
}
// end main
实例
源码地址- https://github.com/tarickb/the-geek-in-the-corner
用法
[root@localhost 01_basic-client-server]# ./server
listening on port 42956.
client <server-address> <server-port>
Makefile
.PHONY: clean
CFLAGS := -Wall -g
LDLIBS := ${LDLIBS} -lrdmacm -libverbs -lpthread
APPS := server client
all: ${APPS}
clean:
rm -f ${APPS}
注意:makefile 没有-L 指定lib的路径,所以 -lrdmacm -libverbs -lpthread 对应的库 librdmacm.so libibverbs.so libpthread.so 应放在默认的路径下/usr/lib 或/usr/lib64
服务端server.c:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <rdma/rdma_cma.h>#define TEST_NZ(x) do { if ( (x)) die("error: " #x " failed (returned non-zero)." ); } while (0)
#define TEST_Z(x) do { if (!(x)) die("error: " #x " failed (returned zero/null)."); } while (0)const int BUFFER_SIZE = 1024;struct context {struct ibv_context *ctx;struct ibv_pd *pd;struct ibv_cq *cq;struct ibv_comp_channel *comp_channel;pthread_t cq_poller_thread;
};struct connection {struct ibv_qp *qp;struct ibv_mr *recv_mr;struct ibv_mr *send_mr;char *recv_region;char *send_region;
};static void die(const char *reason);static void build_context(struct ibv_context *verbs);
static void build_qp_attr(struct ibv_qp_init_attr *qp_attr);
static void * poll_cq(void *);
static void post_receives(struct connection *conn);
static void register_memory(struct connection *conn);static void on_completion(struct ibv_wc *wc);
static int on_connect_request(struct rdma_cm_id *id);
static int on_connection(void *context);
static int on_disconnect(struct rdma_cm_id *id);
static int on_event(struct rdma_cm_event *event);static struct context *s_ctx = NULL;int main(int argc, char **argv)
{
#if _USE_IPV6struct sockaddr_in6 addr;
#elsestruct sockaddr_in addr;
#endifstruct rdma_cm_event *event = NULL;struct rdma_cm_id *listener = NULL;struct rdma_event_channel *ec = NULL;uint16_t port = 0;memset(&addr, 0, sizeof(addr));
#if _USE_IPV6addr.sin6_family = AF_INET6;
#elseaddr.sin_family = AF_INET;
#endifTEST_Z(ec = rdma_create_event_channel());TEST_NZ(rdma_create_id(ec, &listener, NULL, RDMA_PS_TCP));TEST_NZ(rdma_bind_addr(listener, (struct sockaddr *)&addr));TEST_NZ(rdma_listen(listener, 10)); /* backlog=10 is arbitrary */port = ntohs(rdma_get_src_port(listener)); //rdma_get_src_port 返回listener对应的tcp 端口printf("listening on port %d.\n", port);while (rdma_get_cm_event(ec, &event) == 0) {struct rdma_cm_event event_copy;memcpy(&event_copy, event, sizeof(*event));rdma_ack_cm_event(event);if (on_event(&event_copy))break;}rdma_destroy_id(listener);rdma_destroy_event_channel(ec);return 0;
}void die(const char *reason)
{fprintf(stderr, "%s\n", reason);exit(EXIT_FAILURE);
}void build_context(struct ibv_context *verbs)
{if (s_ctx) {if (s_ctx->ctx != verbs)die("cannot handle events in more than one context.");return;}s_ctx = (struct context *)malloc(sizeof(struct context));s_ctx->ctx = verbs;TEST_Z(s_ctx->pd = ibv_alloc_pd(s_ctx->ctx));TEST_Z(s_ctx->comp_channel = ibv_create_comp_channel(s_ctx->ctx));TEST_Z(s_ctx->cq = ibv_create_cq(s_ctx->ctx, 10, NULL, s_ctx->comp_channel, 0)); /* cqe=10 is arbitrary */TEST_NZ(ibv_req_notify_cq(s_ctx->cq, 0)); #完成完成队列与完成通道的关联TEST_NZ(pthread_create(&s_ctx->cq_poller_thread, NULL, poll_cq, NULL));
}void build_qp_attr(struct ibv_qp_init_attr *qp_attr)
{memset(qp_attr, 0, sizeof(*qp_attr));qp_attr->send_cq = s_ctx->cq;qp_attr->recv_cq = s_ctx->cq;qp_attr->qp_type = IBV_QPT_RC;qp_attr->cap.max_send_wr = 10;qp_attr->cap.max_recv_wr = 10;qp_attr->cap.max_send_sge = 1;qp_attr->cap.max_recv_sge = 1;
}void * poll_cq(void *ctx)
{struct ibv_cq *cq;struct ibv_wc wc;while (1) {TEST_NZ(ibv_get_cq_event(s_ctx->comp_channel, &cq, &ctx));ibv_ack_cq_events(cq, 1);TEST_NZ(ibv_req_notify_cq(cq, 0));while (ibv_poll_cq(cq, 1, &wc))on_completion(&wc);}return NULL;
}void post_receives(struct connection *conn)
{struct ibv_recv_wr wr, *bad_wr = NULL;struct ibv_sge sge;wr.wr_id = (uintptr_t)conn;wr.next = NULL;wr.sg_list = &sge;wr.num_sge = 1;sge.addr = (uintptr_t)conn->recv_region;sge.length = BUFFER_SIZE;sge.lkey = conn->recv_mr->lkey;TEST_NZ(ibv_post_recv(conn->qp, &wr, &bad_wr));
}void register_memory(struct connection *conn)
{conn->send_region = malloc(BUFFER_SIZE);conn->recv_region = malloc(BUFFER_SIZE);TEST_Z(conn->send_mr = ibv_reg_mr(s_ctx->pd,conn->send_region,BUFFER_SIZE,0));TEST_Z(conn->recv_mr = ibv_reg_mr(s_ctx->pd,conn->recv_region,BUFFER_SIZE,IBV_ACCESS_LOCAL_WRITE));
}void on_completion(struct ibv_wc *wc)
{if (wc->status != IBV_WC_SUCCESS)die("on_completion: status is not IBV_WC_SUCCESS.");if (wc->opcode & IBV_WC_RECV) {struct connection *conn = (struct connection *)(uintptr_t)wc->wr_id;printf("received message: %s\n", conn->recv_region);} else if (wc->opcode == IBV_WC_SEND) {printf("send completed successfully.\n");}
}int on_connect_request(struct rdma_cm_id *id)
{struct ibv_qp_init_attr qp_attr;struct rdma_conn_param cm_params;struct connection *conn;printf("received connection request.\n");build_context(id->verbs);build_qp_attr(&qp_attr);TEST_NZ(rdma_create_qp(id, s_ctx->pd, &qp_attr));id->context = conn = (struct connection *)malloc(sizeof(struct connection));conn->qp = id->qp;register_memory(conn);post_receives(conn);memset(&cm_params, 0, sizeof(cm_params));TEST_NZ(rdma_accept(id, &cm_params));return 0;
}int on_connection(void *context)
{struct connection *conn = (struct connection *)context;struct ibv_send_wr wr, *bad_wr = NULL;struct ibv_sge sge;snprintf(conn->send_region, BUFFER_SIZE, "message from passive/server side with pid %d", getpid());printf("connected. posting send...\n");memset(&wr, 0, sizeof(wr));wr.opcode = IBV_WR_SEND;wr.sg_list = &sge;wr.num_sge = 1;wr.send_flags = IBV_SEND_SIGNALED;sge.addr = (uintptr_t)conn->send_region;sge.length = BUFFER_SIZE;sge.lkey = conn->send_mr->lkey;TEST_NZ(ibv_post_send(conn->qp, &wr, &bad_wr));return 0;
}int on_disconnect(struct rdma_cm_id *id)
{struct connection *conn = (struct connection *)id->context;printf("peer disconnected.\n");rdma_destroy_qp(id);ibv_dereg_mr(conn->send_mr);ibv_dereg_mr(conn->recv_mr);free(conn->send_region);free(conn->recv_region);free(conn);rdma_destroy_id(id);return 0;
}int on_event(struct rdma_cm_event *event)
{int r = 0;if (event->event == RDMA_CM_EVENT_CONNECT_REQUEST)r = on_connect_request(event->id);else if (event->event == RDMA_CM_EVENT_ESTABLISHED)r = on_connection(event->id->context);else if (event->event == RDMA_CM_EVENT_DISCONNECTED)r = on_disconnect(event->id);elsedie("on_event: unknown event.");return r;
}
客户端client.c:
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <rdma/rdma_cma.h>#define TEST_NZ(x) do { if ( (x)) die("error: " #x " failed (returned non-zero)." ); } while (0)
#define TEST_Z(x) do { if (!(x)) die("error: " #x " failed (returned zero/null)."); } while (0)const int BUFFER_SIZE = 1024;
const int TIMEOUT_IN_MS = 500; /* ms */struct context {struct ibv_context *ctx;struct ibv_pd *pd;struct ibv_cq *cq;struct ibv_comp_channel *comp_channel;pthread_t cq_poller_thread;
};struct connection {struct rdma_cm_id *id;struct ibv_qp *qp;struct ibv_mr *recv_mr;struct ibv_mr *send_mr;char *recv_region;char *send_region;int num_completions;
};static void die(const char *reason);static void build_context(struct ibv_context *verbs);
static void build_qp_attr(struct ibv_qp_init_attr *qp_attr);
static void * poll_cq(void *);
static void post_receives(struct connection *conn);
static void register_memory(struct connection *conn);static int on_addr_resolved(struct rdma_cm_id *id);
static void on_completion(struct ibv_wc *wc);
static int on_connection(void *context);
static int on_disconnect(struct rdma_cm_id *id);
static int on_event(struct rdma_cm_event *event);
static int on_route_resolved(struct rdma_cm_id *id);static struct context *s_ctx = NULL;int main(int argc, char **argv)
{struct addrinfo *addr;struct rdma_cm_event *event = NULL;struct rdma_cm_id *conn= NULL;struct rdma_event_channel *ec = NULL;if (argc != 3)die("usage: client <server-address> <server-port>");TEST_NZ(getaddrinfo(argv[1], argv[2], NULL, &addr));TEST_Z(ec = rdma_create_event_channel());TEST_NZ(rdma_create_id(ec, &conn, NULL, RDMA_PS_TCP));TEST_NZ(rdma_resolve_addr(conn, NULL, addr->ai_addr, TIMEOUT_IN_MS));freeaddrinfo(addr);while (rdma_get_cm_event(ec, &event) == 0) {struct rdma_cm_event event_copy;memcpy(&event_copy, event, sizeof(*event));rdma_ack_cm_event(event);if (on_event(&event_copy))break;}rdma_destroy_event_channel(ec);return 0;
}void die(const char *reason)
{fprintf(stderr, "%s\n", reason);exit(EXIT_FAILURE);
}void build_context(struct ibv_context *verbs)
{if (s_ctx) {if (s_ctx->ctx != verbs)die("cannot handle events in more than one context.");return;}s_ctx = (struct context *)malloc(sizeof(struct context));s_ctx->ctx = verbs;TEST_Z(s_ctx->pd = ibv_alloc_pd(s_ctx->ctx));TEST_Z(s_ctx->comp_channel = ibv_create_comp_channel(s_ctx->ctx));TEST_Z(s_ctx->cq = ibv_create_cq(s_ctx->ctx, 10, NULL, s_ctx->comp_channel, 0)); /* cqe=10 is arbitrary */TEST_NZ(ibv_req_notify_cq(s_ctx->cq, 0));TEST_NZ(pthread_create(&s_ctx->cq_poller_thread, NULL, poll_cq, NULL));
}void build_qp_attr(struct ibv_qp_init_attr *qp_attr)
{memset(qp_attr, 0, sizeof(*qp_attr));qp_attr->send_cq = s_ctx->cq;qp_attr->recv_cq = s_ctx->cq;qp_attr->qp_type = IBV_QPT_RC;qp_attr->cap.max_send_wr = 10;qp_attr->cap.max_recv_wr = 10;qp_attr->cap.max_send_sge = 1;qp_attr->cap.max_recv_sge = 1;
}void * poll_cq(void *ctx)
{struct ibv_cq *cq;struct ibv_wc wc;while (1) {TEST_NZ(ibv_get_cq_event(s_ctx->comp_channel, &cq, &ctx));ibv_ack_cq_events(cq, 1);TEST_NZ(ibv_req_notify_cq(cq, 0));while (ibv_poll_cq(cq, 1, &wc))on_completion(&wc);}return NULL;
}void post_receives(struct connection *conn)
{struct ibv_recv_wr wr, *bad_wr = NULL;struct ibv_sge sge;wr.wr_id = (uintptr_t)conn;wr.next = NULL;wr.sg_list = &sge;wr.num_sge = 1;sge.addr = (uintptr_t)conn->recv_region;sge.length = BUFFER_SIZE;sge.lkey = conn->recv_mr->lkey;TEST_NZ(ibv_post_recv(conn->qp, &wr, &bad_wr));
}void register_memory(struct connection *conn)
{conn->send_region = malloc(BUFFER_SIZE);conn->recv_region = malloc(BUFFER_SIZE);TEST_Z(conn->send_mr = ibv_reg_mr(s_ctx->pd, conn->send_region, BUFFER_SIZE, 0));TEST_Z(conn->recv_mr = ibv_reg_mr(s_ctx->pd, conn->recv_region, BUFFER_SIZE, IBV_ACCESS_LOCAL_WRITE));
}int on_addr_resolved(struct rdma_cm_id *id)
{struct ibv_qp_init_attr qp_attr;struct connection *conn;printf("address resolved.\n");build_context(id->verbs);build_qp_attr(&qp_attr);TEST_NZ(rdma_create_qp(id, s_ctx->pd, &qp_attr));id->context = conn = (struct connection *)malloc(sizeof(struct connection));conn->id = id;conn->qp = id->qp;conn->num_completions = 0;register_memory(conn);post_receives(conn);TEST_NZ(rdma_resolve_route(id, TIMEOUT_IN_MS));return 0;
}void on_completion(struct ibv_wc *wc)
{struct connection *conn = (struct connection *)(uintptr_t)wc->wr_id;if (wc->status != IBV_WC_SUCCESS)die("on_completion: status is not IBV_WC_SUCCESS.");if (wc->opcode & IBV_WC_RECV)printf("received message: %s\n", conn->recv_region);else if (wc->opcode == IBV_WC_SEND)printf("send completed successfully.\n");elsedie("on_completion: completion isn't a send or a receive.");if (++conn->num_completions == 2)rdma_disconnect(conn->id);
}int on_connection(void *context)
{struct connection *conn = (struct connection *)context;struct ibv_send_wr wr, *bad_wr = NULL;struct ibv_sge sge;snprintf(conn->send_region, BUFFER_SIZE, "message from active/client side with pid %d", getpid());printf("connected. posting send...\n");memset(&wr, 0, sizeof(wr));wr.wr_id = (uintptr_t)conn;wr.opcode = IBV_WR_SEND;wr.sg_list = &sge;wr.num_sge = 1;wr.send_flags = IBV_SEND_SIGNALED;sge.addr = (uintptr_t)conn->send_region;sge.length = BUFFER_SIZE;sge.lkey = conn->send_mr->lkey;TEST_NZ(ibv_post_send(conn->qp, &wr, &bad_wr));return 0;
}int on_disconnect(struct rdma_cm_id *id)
{struct connection *conn = (struct connection *)id->context;printf("disconnected.\n");rdma_destroy_qp(id);ibv_dereg_mr(conn->send_mr);ibv_dereg_mr(conn->recv_mr);free(conn->send_region);free(conn->recv_region);free(conn);rdma_destroy_id(id);return 1; /* exit event loop */
}int on_event(struct rdma_cm_event *event)
{int r = 0;if (event->event == RDMA_CM_EVENT_ADDR_RESOLVED)r = on_addr_resolved(event->id);else if (event->event == RDMA_CM_EVENT_ROUTE_RESOLVED)r = on_route_resolved(event->id);else if (event->event == RDMA_CM_EVENT_ESTABLISHED)r = on_connection(event->id->context);else if (event->event == RDMA_CM_EVENT_DISCONNECTED)r = on_disconnect(event->id);elsedie("on_event: unknown event.");return r;
}int on_route_resolved(struct rdma_cm_id *id)
{struct rdma_conn_param cm_params;printf("route resolved.\n");memset(&cm_params, 0, sizeof(cm_params));TEST_NZ(rdma_connect(id, &cm_params));return 0;
}
更多讲解教程
InfiniBand, Verbs, RDMA | https://thegeekinthecorner.wordpress.com/category/infiniband-verbs-rdma/
RDMA read and write with IB verbs | https://thegeekinthecorner.wordpress.com/2010/09/28/rdma-read-and-write-with-ib-verbs/
http://www.hpcadvisorycouncil.com/pdf/building-an-rdma-capable-application-with-ib-verbs.pdf
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