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

[Tonghao Zhang <xiangxia.m.yue@gmail.com>]

On Thu, Mar 29, 2018 at 3:32 PM, Tan, Jianfeng <jianfeng.tan@intel.com> wrote:
> Hi Xiangxia,
>
>> -----Original Message-----
>> From: xiangxia.m.yue@gmail.com [mailto:xiangxia.m.yue@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.yue@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.yue@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.


> 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
>