From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Tan, Jianfeng" <jianfeng.tan@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Burakov, Anatoly" <anatoly.burakov@intel.com>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>,
"thomas@monjalon.net" <thomas@monjalon.net>
Subject: Re: [dpdk-dev] [PATCH v2 3/4] eal: add synchronous multi-process communication
Date: Wed, 17 Jan 2018 10:50:22 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB9772588627EE16@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <f388e217-7acf-684a-dd98-cf33f421d2fb@intel.com>
> > Hi Jianfeng,
> >
> >> -----Original Message-----
> >> From: Tan, Jianfeng
> >> Sent: Tuesday, January 16, 2018 8:11 AM
> >> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>; dev@dpdk.org; Burakov, Anatoly <anatoly.burakov@intel.com>
> >> Cc: Richardson, Bruce <bruce.richardson@intel.com>; thomas@monjalon.net
> >> Subject: Re: [PATCH v2 3/4] eal: add synchronous multi-process communication
> >>
> >> Thank you, Konstantin and Anatoly firstly. Other comments are well
> >> received and I'll send out a new version.
> >>
> >>
> >> On 1/16/2018 8:00 AM, Ananyev, Konstantin wrote:
> >>>> We need the synchronous way for multi-process communication,
> >>>> i.e., blockingly waiting for reply message when we send a request
> >>>> to the peer process.
> >>>>
> >>>> We add two APIs rte_eal_mp_request() and rte_eal_mp_reply() for
> >>>> such use case. By invoking rte_eal_mp_request(), a request message
> >>>> is sent out, and then it waits there for a reply message. The
> >>>> timeout is hard-coded 5 Sec. And the replied message will be copied
> >>>> in the parameters of this API so that the caller can decide how
> >>>> to translate those information (including params and fds). Note
> >>>> if a primary process owns multiple secondary processes, this API
> >>>> will fail.
> >>>>
> >>>> The API rte_eal_mp_reply() is always called by an mp action handler.
> >>>> Here we add another parameter for rte_eal_mp_t so that the action
> >>>> handler knows which peer address to reply.
> >>>>
> >>>> We use mutex in rte_eal_mp_request() to guarantee that only one
> >>>> request is on the fly for one pair of processes.
> >>> You don't need to do things in such strange and restrictive way.
> >>> Instead you can do something like that:
> >>> 1) Introduce new struct, list for it and mutex
> >>> struct sync_request {
> >>> int reply_received;
> >>> char dst[PATH_MAX];
> >>> char reply[...];
> >>> LIST_ENTRY(sync_request) next;
> >>> };
> >>>
> >>> static struct
> >>> LIST_HEAD(list, sync_request);
> >>> pthread_mutex_t lock;
> >>> pthead_cond_t cond;
> >>> } sync_requests;
> >>>
> >>> 2) then at request() call:
> >>> Grab sync_requests.lock
> >>> Check do we already have a pending request for that destination,
> >>> If yes - the release the lock and returns with error.
> >>> - allocate and init new sync_request struct, set reply_received=0
> >>> - do send_msg()
> >>> -then in a cycle:
> >>> pthread_cond_timed_wait(&sync_requests.cond, &sync_request.lock, ×pec);
> >>> - at return from it check if sync_request.reply_received == 1, if not
> >>> check if timeout expired and either return a failure or go to the start of the cycle.
> >>>
> >>> 3) at mp_handler() if REPLY received - grab sync_request.lock,
> >>> search through sync_requests.list for dst[] ,
> >>> if found, then set it's reply_received=1, copy the received message into reply
> >>> and call pthread_cond_braodcast((&sync_requests.cond);
> >> The only benefit I can see is that now the sender can request to
> >> multiple receivers at the same time. And it makes things more
> >> complicated. Do we really need this?
> > The benefit is that one thread is blocked waiting for response,
> > your mp_handler can still receive and handle other messages.
>
> This can already be done in the original implementation. mp_handler
> listens for msg, request from the other peer(s), and replies the
> requests, which is not affected.
>
> > Plus as you said - other threads can keep sending messages.
>
> For this one, in the original implementation, other threads can still
> send msg, but not request. I suppose the request is not in a fast path,
> why we care to make it fast?
>
+int
+rte_eal_mp_request(const char *action_name,
+ void *params,
+ int len_p,
+ int fds[],
+ int fds_in,
+ int fds_out)
+{
+ int i, j;
+ int sockfd;
+ int nprocs;
+ int ret = 0;
+ struct mp_msghdr *req;
+ struct timeval tv;
+ char buf[MAX_MSG_LENGTH];
+ struct mp_msghdr *hdr;
+
+ RTE_LOG(DEBUG, EAL, "request: %s\n", action_name);
+
+ if (fds_in > SCM_MAX_FD || fds_out > SCM_MAX_FD) {
+ RTE_LOG(ERR, EAL, "Cannot send more than %d FDs\n", SCM_MAX_FD);
+ rte_errno = -E2BIG;
+ return 0;
+ }
+
+ req = format_msg(action_name, params, len_p, fds_in, MP_REQ);
+ if (req == NULL)
+ return 0;
+
+ if ((sockfd = open_unix_fd(0)) < 0) {
+ free(req);
+ return 0;
+ }
+
+ tv.tv_sec = 5; /* 5 Secs Timeout */
+ tv.tv_usec = 0;
+ if (setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO,
+ (const void *)&tv, sizeof(struct timeval)) < 0)
+ RTE_LOG(INFO, EAL, "Failed to set recv timeout\n");
I f you set it just for one call, why do you not restore it?
Also I don't think it is a good idea to change it here -
if you'll make timeout a parameter value - then it could be overwritten
by different threads.
+
+ /* Only allow one req at a time */
+ pthread_mutex_lock(&mp_mutex_request);
+
+ if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
+ nprocs = 0;
+ for (i = 0; i < MAX_SECONDARY_PROCS; ++i)
+ if (!mp_sec_sockets[i]) {
+ j = i;
+ nprocs++;
+ }
+
+ if (nprocs > 1) {
+ RTE_LOG(ERR, EAL,
+ "multi secondary processes not supported\n");
+ goto free_and_ret;
+ }
+
+ ret = send_msg(sockfd, mp_sec_sockets[j], req, fds);
As I remember - sndmsg() is also blocking call, so under some conditions you can stall
there forever.
As mp_mutex_requestis still held - next rte_eal_mp_request(0 will also block forever here.
+ } else
+ ret = send_msg(sockfd, eal_mp_unix_path(), req, fds);
+
+ if (ret == 0) {
+ RTE_LOG(ERR, EAL, "failed to send request: %s\n", action_name);
+ ret = -1;
+ goto free_and_ret;
+ }
+
+ ret = read_msg(sockfd, buf, MAX_MSG_LENGTH, fds, fds_out, NULL);
if the message you receive is not a reply you are expecting -
it will be simply dropped - mp_handler() would never process it.
+ if (ret > 0) {
+ hdr = (struct mp_msghdr *)buf;
+ if (hdr->len_params == len_p)
+ memcpy(params, hdr->params, len_p);
+ else {
+ RTE_LOG(ERR, EAL, "invalid reply\n");
+ ret = 0;
+ }
+ }
+
+free_and_ret:
+ free(req);
+ close(sockfd);
+ pthread_mutex_unlock(&mp_mutex_request);
+ return ret;
+}
All of the above makes me think that current implementation is erroneous
and needs to be reworked.
Konstantin
next prev parent reply other threads:[~2018-01-17 10:50 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 18:44 [dpdk-dev] [PATCH 0/3] generic channel for " Jianfeng Tan
2017-11-30 18:44 ` [dpdk-dev] [PATCH 1/3] eal: add " Jianfeng Tan
2017-12-11 11:04 ` Burakov, Anatoly
2017-12-11 16:43 ` Ananyev, Konstantin
2017-11-30 18:44 ` [dpdk-dev] [PATCH 2/3] eal: add synchronous " Jianfeng Tan
2017-12-11 11:39 ` Burakov, Anatoly
2017-12-11 16:49 ` Ananyev, Konstantin
2017-11-30 18:44 ` [dpdk-dev] [PATCH 3/3] vfio: use the generic multi-process channel Jianfeng Tan
2017-12-11 12:01 ` Burakov, Anatoly
2017-12-11 9:59 ` [dpdk-dev] [PATCH 0/3] generic channel for multi-process communication Burakov, Anatoly
2017-12-12 7:34 ` Tan, Jianfeng
2017-12-12 16:18 ` Burakov, Anatoly
2018-01-11 4:07 ` [dpdk-dev] [PATCH v2 0/4] " Jianfeng Tan
2018-01-11 4:07 ` [dpdk-dev] [PATCH v2 1/4] eal: add " Jianfeng Tan
2018-01-13 12:57 ` Burakov, Anatoly
2018-01-15 19:52 ` Ananyev, Konstantin
2018-01-11 4:07 ` [dpdk-dev] [PATCH v2 2/4] eal: add and del secondary processes in the primary Jianfeng Tan
2018-01-13 13:11 ` Burakov, Anatoly
2018-01-15 21:45 ` Ananyev, Konstantin
2018-01-11 4:07 ` [dpdk-dev] [PATCH v2 3/4] eal: add synchronous multi-process communication Jianfeng Tan
2018-01-13 13:41 ` Burakov, Anatoly
2018-01-16 0:00 ` Ananyev, Konstantin
2018-01-16 8:10 ` Tan, Jianfeng
2018-01-16 11:12 ` Ananyev, Konstantin
2018-01-16 16:47 ` Tan, Jianfeng
2018-01-17 10:50 ` Ananyev, Konstantin [this message]
2018-01-17 13:09 ` Tan, Jianfeng
2018-01-17 13:15 ` Tan, Jianfeng
2018-01-17 17:20 ` Ananyev, Konstantin
2018-01-11 4:07 ` [dpdk-dev] [PATCH v2 4/4] vfio: use the generic multi-process channel Jianfeng Tan
2018-01-13 14:03 ` Burakov, Anatoly
2018-03-04 14:57 ` [dpdk-dev] [PATCH v5] vfio: change to use " Jianfeng Tan
2018-03-14 13:27 ` Burakov, Anatoly
2018-03-19 6:53 ` Tan, Jianfeng
2018-03-20 10:33 ` Burakov, Anatoly
2018-03-20 10:56 ` Burakov, Anatoly
2018-03-20 8:50 ` [dpdk-dev] [PATCH v6] " Jianfeng Tan
2018-04-05 14:26 ` Tan, Jianfeng
2018-04-05 14:39 ` Burakov, Anatoly
2018-04-12 23:27 ` Thomas Monjalon
2018-04-12 15:26 ` Burakov, Anatoly
2018-04-15 15:06 ` [dpdk-dev] [PATCH v7] " Jianfeng Tan
2018-04-15 15:10 ` Tan, Jianfeng
2018-04-17 23:04 ` Thomas Monjalon
2018-01-25 4:16 ` [dpdk-dev] [PATCH v3 0/3] generic channel for multi-process communication Jianfeng Tan
2018-01-25 4:16 ` [dpdk-dev] [PATCH v3 1/3] eal: add " Jianfeng Tan
2018-01-25 10:41 ` Thomas Monjalon
2018-01-25 11:27 ` Burakov, Anatoly
2018-01-25 11:34 ` Thomas Monjalon
2018-01-25 12:21 ` Ananyev, Konstantin
2018-01-25 4:16 ` [dpdk-dev] [PATCH v3 2/3] eal: add synchronous " Jianfeng Tan
2018-01-25 12:00 ` Burakov, Anatoly
2018-01-25 12:19 ` Burakov, Anatoly
2018-01-25 12:19 ` Ananyev, Konstantin
2018-01-25 12:25 ` Burakov, Anatoly
2018-01-25 13:00 ` Ananyev, Konstantin
2018-01-25 13:05 ` Burakov, Anatoly
2018-01-25 13:10 ` Burakov, Anatoly
2018-01-25 15:03 ` Ananyev, Konstantin
2018-01-25 16:22 ` Burakov, Anatoly
2018-01-25 17:10 ` Tan, Jianfeng
2018-01-25 18:02 ` Burakov, Anatoly
2018-01-25 12:22 ` Ananyev, Konstantin
2018-01-25 4:16 ` [dpdk-dev] [PATCH v3 3/3] vfio: use the generic multi-process channel Jianfeng Tan
2018-01-25 10:47 ` Thomas Monjalon
2018-01-25 10:52 ` Burakov, Anatoly
2018-01-25 10:57 ` Thomas Monjalon
2018-01-25 12:15 ` Burakov, Anatoly
2018-01-25 19:14 ` [dpdk-dev] [PATCH v4 0/2] generic channel for multi-process communication Jianfeng Tan
2018-01-25 19:14 ` [dpdk-dev] [PATCH v4 1/2] eal: add synchronous " Jianfeng Tan
2018-01-25 19:14 ` [dpdk-dev] [PATCH v4 2/2] vfio: use the generic multi-process channel Jianfeng Tan
2018-01-25 19:15 ` [dpdk-dev] [PATCH v4 0/2] generic channel for multi-process communication Tan, Jianfeng
2018-01-25 19:21 ` [dpdk-dev] [PATCH v5 " Jianfeng Tan
2018-01-25 19:21 ` [dpdk-dev] [PATCH v5 1/2] eal: add " Jianfeng Tan
2018-01-25 19:21 ` [dpdk-dev] [PATCH v5 2/2] eal: add synchronous " Jianfeng Tan
2018-01-25 21:23 ` [dpdk-dev] [PATCH v5 0/2] generic channel for " Thomas Monjalon
2018-01-26 3:41 ` [dpdk-dev] [PATCH v6 " Jianfeng Tan
2018-01-26 3:41 ` [dpdk-dev] [PATCH v6 1/2] eal: add " Jianfeng Tan
2018-01-26 10:25 ` Burakov, Anatoly
2018-01-29 6:37 ` Tan, Jianfeng
2018-01-29 9:37 ` Burakov, Anatoly
2018-01-26 3:41 ` [dpdk-dev] [PATCH v6 2/2] eal: add synchronous " Jianfeng Tan
2018-01-26 10:31 ` Burakov, Anatoly
2018-01-29 23:52 ` [dpdk-dev] [PATCH v6 0/2] generic channel for " Thomas Monjalon
2018-01-30 6:58 ` [dpdk-dev] [PATCH v7 " Jianfeng Tan
2018-01-30 6:58 ` [dpdk-dev] [PATCH v7 1/2] eal: add " Jianfeng Tan
2018-01-30 6:58 ` [dpdk-dev] [PATCH v7 2/2] eal: add synchronous " Jianfeng Tan
2018-01-30 14:46 ` [dpdk-dev] [PATCH v7 0/2] generic channel for " Thomas Monjalon
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