Re: [dpdk-dev] [PATCH 2/2] vhost: add pipe event for optimizing negotiating

[Maxime Coquelin]

Hi Xiangxia,

On 03/29/2018 01:24 PM, Tonghao Zhang wrote:
On Thu, Mar 29, 2018 at 3:32 PM, Tan, Jianfeng <jianfeng....@intel.com> wrote:
Hi Xiangxia,
-----Original Message-----
From: xiangxia.m....@gmail.com [mailto:xiangxia.m....@gmail.com]
Sent: Wednesday, March 28, 2018 1:49 PM
To: Tan, Jianfeng
Cc: dev@dpdk.org; Tonghao Zhang
Subject: [PATCH 2/2] vhost: add pipe event for optimizing negotiating

From: Tonghao Zhang <xiangxia.m....@gmail.com>

When vhost—user connects qemu successfully, dpdk will call

Typo: "-"
v2 will update it. :)

the vhost_user_add_connection to add unix socket fd to poll.
And fdset_add only set the socket fd to a fdentry while poll
may sleep now. In a general case, this is no problem. But if
we use hot update for vhost-user, most downtime of VMs network
is 750+ms. This patch adds pipe event, so after connections are
ok, dpdk rebuild the poll immediately. With this patch, the
most downtime is 20~30ms.

Signed-off-by: Tonghao Zhang <xiangxia.m....@gmail.com>
---
  lib/librte_vhost/fd_man.c | 49
+++++++++++++++++++++++++++++++++++++++++++++++
  lib/librte_vhost/fd_man.h | 16 ++++++++++++++++
  lib/librte_vhost/socket.c | 14 ++++++++++++++
  3 files changed, 79 insertions(+)

diff --git a/lib/librte_vhost/fd_man.c b/lib/librte_vhost/fd_man.c
index 181711c..7716757 100644
--- a/lib/librte_vhost/fd_man.c
+++ b/lib/librte_vhost/fd_man.c
@@ -15,6 +15,7 @@
  #include <rte_log.h>

  #include "fd_man.h"
+#include "vhost.h"

This is a nice finding and solution, however, I don't think we shall include 
vhost header file in fd related files. Actually, I did not find out why you 
need to include this header file.

Hi Jianfeng, thanks for your review. In the fdset_pipe_init function,
I call the RTE_LOG with VHOST_CONFIG, when init pipe not successfully.
So I included the vhost header file.

Maybe better to create VHOST_SOCKET in socket.c, than including vhost.h 
that creates a layer violation:

#define RTE_LOGTYPE_VHOST_SOCKET RTE_LOGTYPE_USER1

Is it Ok for you? I so no need to resend, I can handle the change when
applying.

Thanks,
Maxime


Thanks,
Jianfeng


  #define FDPOLLERR (POLLERR | POLLHUP | POLLNVAL)

@@ -272,3 +273,51 @@

       return NULL;
  }
+
+static void
+fdset_pipe_read_cb(int readfd, void *dat __rte_unused,
+                int *remove __rte_unused)
+{
+     char charbuf[16];
+     read(readfd, charbuf, sizeof(charbuf));
+}
+
+void
+fdset_pipe_uninit(struct fdset *fdset)
+{
+     fdset_del(fdset, fdset->u.readfd);
+     close(fdset->u.readfd);
+     close(fdset->u.writefd);
+}
+
+int
+fdset_pipe_init(struct fdset *fdset)
+{
+     int ret;
+
+     if (pipe(fdset->u.pipefd) < 0) {
+             RTE_LOG(ERR, VHOST_CONFIG,
+                     "failed to create pipe for vhost fdset\n");
+             return -1;
+     }
+
+     ret = fdset_add(fdset, fdset->u.readfd,
+                     fdset_pipe_read_cb, NULL, NULL);
+
+     if (ret < 0) {
+             RTE_LOG(ERR, VHOST_CONFIG,
+                     "failed to add pipe readfd %d into vhost server
fdset\n",
+                     fdset->u.readfd);
+
+             fdset_pipe_uninit(fdset);
+             return -1;
+     }
+
+     return 0;
+}
+
+void
+fdset_pipe_notify(struct fdset *fdset)
+{
+     write(fdset->u.writefd, "1", 1);
+}
diff --git a/lib/librte_vhost/fd_man.h b/lib/librte_vhost/fd_man.h
index 3a9276c..76a42fb 100644
--- a/lib/librte_vhost/fd_man.h
+++ b/lib/librte_vhost/fd_man.h
@@ -25,6 +25,16 @@ struct fdset {
       struct fdentry fd[MAX_FDS];
       pthread_mutex_t fd_mutex;
       int num;        /* current fd number of this fdset */
+
+     union pipefds {
+             struct {
+                     int pipefd[2];
+             };
+             struct {
+                     int readfd;
+                     int writefd;
+             };
+     } u;
  };


@@ -37,4 +47,10 @@ int fdset_add(struct fdset *pfdset, int fd,

  void *fdset_event_dispatch(void *arg);

+int fdset_pipe_init(struct fdset *fdset);
+
+void fdset_pipe_uninit(struct fdset *fdset);
+
+void fdset_pipe_notify(struct fdset *fdset);
+
  #endif
diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index 95bed78..795239c 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -231,6 +231,8 @@ struct vhost_user {
       pthread_mutex_lock(&vsocket->conn_mutex);
       TAILQ_INSERT_TAIL(&vsocket->conn_list, conn, next);
       pthread_mutex_unlock(&vsocket->conn_mutex);
+
+     fdset_pipe_notify(&vhost_user.fdset);
       return;

  err:
@@ -829,11 +831,23 @@ struct vhost_device_ops const *
               return -1;

       if (fdset_tid == 0) {
+             /**
+              * create a pipe which will be waited by poll and notified to
+              * rebuild the wait list of poll.
+              */
+             if (fdset_pipe_init(&vhost_user.fdset) < 0) {
+                     RTE_LOG(ERR, VHOST_CONFIG,
+                             "failed to create pipe for vhost fdset\n");
+                     return -1;
+             }
+
               int ret = pthread_create(&fdset_tid, NULL, fdset_event_dispatch,
                                    &vhost_user.fdset);
               if (ret != 0) {
                       RTE_LOG(ERR, VHOST_CONFIG,
                               "failed to create fdset handling thread");
+
+                     fdset_pipe_uninit(&vhost_user.fdset);
                       return -1;
               } else {
                       snprintf(thread_name, RTE_MAX_THREAD_NAME_LEN,
--
1.8.3.1