From: Chenbo Xia <chenbox@nvidia.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
David Marchand <david.marchand@redhat.com>
Subject: Re: [PATCH v3 5/5] vhost: manage FD with epoll
Date: Sun, 28 Apr 2024 03:22:09 +0000 [thread overview]
Message-ID: <B677E726-2C99-4734-9363-2A2D1C09611E@nvidia.com> (raw)
In-Reply-To: <20240409114845.1336403-6-maxime.coquelin@redhat.com>
Hi Maxime,
> On Apr 9, 2024, at 19:48, Maxime Coquelin <maxime.coquelin@redhat.com> wrote:
>
> External email: Use caution opening links or attachments
>
>
> From: David Marchand <david.marchand@redhat.com>
>
> Switch to epoll so that the concern over the poll() fd array
> is removed.
> Add a simple list of used entries and track the next free entry.
>
> epoll() is thread safe, we no more need a synchronization
> mechanism and so can remove the notification pipe.
>
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
> lib/vhost/fd_man.c | 399 ++++++++++++---------------------------------
> lib/vhost/fd_man.h | 5 +-
> 2 files changed, 106 insertions(+), 298 deletions(-)
>
> diff --git a/lib/vhost/fd_man.c b/lib/vhost/fd_man.c
> index 8b47c97d45..a4a2965da1 100644
> --- a/lib/vhost/fd_man.c
> +++ b/lib/vhost/fd_man.c
> @@ -3,9 +3,9 @@
> */
>
> #include <errno.h>
> -#include <pthread.h>
> #include <stdio.h>
> #include <string.h>
> +#include <sys/epoll.h>
> #include <unistd.h>
>
> #include <rte_common.h>
> @@ -21,49 +21,34 @@ RTE_LOG_REGISTER_SUFFIX(vhost_fdset_logtype, fdset, INFO);
> #define VHOST_FDMAN_LOG(level, ...) \
> RTE_LOG_LINE(level, VHOST_FDMAN, "" __VA_ARGS__)
>
> -#define FDPOLLERR (POLLERR | POLLHUP | POLLNVAL)
> -
> struct fdentry {
> int fd; /* -1 indicates this entry is empty */
> fd_cb rcb; /* callback when this fd is readable. */
> fd_cb wcb; /* callback when this fd is writeable.*/
> void *dat; /* fd context */
> int busy; /* whether this entry is being used in cb. */
> + LIST_ENTRY(fdentry) next;
> };
>
> struct fdset {
> char name[RTE_THREAD_NAME_SIZE];
> - struct pollfd rwfds[MAX_FDS];
> + int epfd;
> struct fdentry fd[MAX_FDS];
> + LIST_HEAD(, fdentry) fdlist;
> + int next_free_idx;
> rte_thread_t tid;
> pthread_mutex_t fd_mutex;
> - pthread_mutex_t fd_polling_mutex;
> - int num; /* current fd number of this fdset */
> -
> - union pipefds {
> - struct {
> - int pipefd[2];
> - };
> - struct {
> - int readfd;
> - int writefd;
> - };
> - } u;
> -
> - pthread_mutex_t sync_mutex;
> - pthread_cond_t sync_cond;
> - bool sync;
> +
Not sure this blank line is intended or not :)
> bool destroy;
> };
>
> -static int fdset_add_no_sync(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat);
> -static uint32_t fdset_event_dispatch(void *arg);
> -
> #define MAX_FDSETS 8
>
> static struct fdset *fdsets[MAX_FDSETS];
> pthread_mutex_t fdsets_mutex = PTHREAD_MUTEX_INITIALIZER;
>
> +static uint32_t fdset_event_dispatch(void *arg);
> +
> static struct fdset *
> fdset_lookup(const char *name)
> {
> @@ -96,166 +81,6 @@ fdset_insert(struct fdset *fdset)
> return -1;
> }
>
> -static void
> -fdset_pipe_read_cb(int readfd, void *dat,
> - int *remove __rte_unused)
> -{
> - char charbuf[16];
> - struct fdset *fdset = dat;
> - int r = read(readfd, charbuf, sizeof(charbuf));
> - /*
> - * Just an optimization, we don't care if read() failed
> - * so ignore explicitly its return value to make the
> - * compiler happy
> - */
> - RTE_SET_USED(r);
> -
> - pthread_mutex_lock(&fdset->sync_mutex);
> - fdset->sync = true;
> - pthread_cond_broadcast(&fdset->sync_cond);
> - pthread_mutex_unlock(&fdset->sync_mutex);
> -}
> -
> -static void
> -fdset_pipe_uninit(struct fdset *fdset)
> -{
> - fdset_del(fdset, fdset->u.readfd);
> - close(fdset->u.readfd);
> - fdset->u.readfd = -1;
> - close(fdset->u.writefd);
> - fdset->u.writefd = -1;
> -}
> -
> -static int
> -fdset_pipe_init(struct fdset *fdset)
> -{
> - int ret;
> -
> - pthread_mutex_init(&fdset->sync_mutex, NULL);
> - pthread_cond_init(&fdset->sync_cond, NULL);
> -
> - if (pipe(fdset->u.pipefd) < 0) {
> - VHOST_FDMAN_LOG(ERR,
> - "failed to create pipe for vhost fdset");
> - return -1;
> - }
> -
> - ret = fdset_add_no_sync(fdset, fdset->u.readfd,
> - fdset_pipe_read_cb, NULL, fdset);
> - if (ret < 0) {
> - VHOST_FDMAN_LOG(ERR,
> - "failed to add pipe readfd %d into vhost server fdset",
> - fdset->u.readfd);
> -
> - fdset_pipe_uninit(fdset);
> - return -1;
> - }
> -
> - return 0;
> -}
> -
> -static void
> -fdset_sync(struct fdset *fdset)
> -{
> - int ret;
> -
> - pthread_mutex_lock(&fdset->sync_mutex);
> -
> - fdset->sync = false;
> - ret = write(fdset->u.writefd, "1", 1);
> - if (ret < 0) {
> - VHOST_FDMAN_LOG(ERR,
> - "Failed to write to notification pipe: %s",
> - strerror(errno));
> - goto out_unlock;
> - }
> -
> - while (!fdset->sync)
> - pthread_cond_wait(&fdset->sync_cond, &fdset->sync_mutex);
> -
> -out_unlock:
> - pthread_mutex_unlock(&fdset->sync_mutex);
> -}
> -
> -static int
> -get_last_valid_idx(struct fdset *pfdset, int last_valid_idx)
> -{
> - int i;
> -
> - for (i = last_valid_idx; i >= 0 && pfdset->fd[i].fd == -1; i--)
> - ;
> -
> - return i;
> -}
> -
> -static void
> -fdset_move(struct fdset *pfdset, int dst, int src)
> -{
> - pfdset->fd[dst] = pfdset->fd[src];
> - pfdset->rwfds[dst] = pfdset->rwfds[src];
> -}
> -
> -static void
> -fdset_shrink_nolock(struct fdset *pfdset)
> -{
> - int i;
> - int last_valid_idx = get_last_valid_idx(pfdset, pfdset->num - 1);
> -
> - for (i = 0; i < last_valid_idx; i++) {
> - if (pfdset->fd[i].fd != -1)
> - continue;
> -
> - fdset_move(pfdset, i, last_valid_idx);
> - last_valid_idx = get_last_valid_idx(pfdset, last_valid_idx - 1);
> - }
> - pfdset->num = last_valid_idx + 1;
> -}
> -
> -/*
> - * Find deleted fd entries and remove them
> - */
> -static void
> -fdset_shrink(struct fdset *pfdset)
> -{
> - pthread_mutex_lock(&pfdset->fd_mutex);
> - fdset_shrink_nolock(pfdset);
> - pthread_mutex_unlock(&pfdset->fd_mutex);
> -}
> -
> -/**
> - * Returns the index in the fdset for a given fd.
> - * @return
> - * index for the fd, or -1 if fd isn't in the fdset.
> - */
> -static int
> -fdset_find_fd(struct fdset *pfdset, int fd)
> -{
> - int i;
> -
> - for (i = 0; i < pfdset->num && pfdset->fd[i].fd != fd; i++)
> - ;
> -
> - return i == pfdset->num ? -1 : i;
> -}
> -
> -static void
> -fdset_add_fd(struct fdset *pfdset, int idx, int fd,
> - fd_cb rcb, fd_cb wcb, void *dat)
> -{
> - struct fdentry *pfdentry = &pfdset->fd[idx];
> - struct pollfd *pfd = &pfdset->rwfds[idx];
> -
> - pfdentry->fd = fd;
> - pfdentry->rcb = rcb;
> - pfdentry->wcb = wcb;
> - pfdentry->dat = dat;
> -
> - pfd->fd = fd;
> - pfd->events = rcb ? POLLIN : 0;
> - pfd->events |= wcb ? POLLOUT : 0;
> - pfd->revents = 0;
> -}
> -
> struct fdset *
> fdset_init(const char *name)
> {
> @@ -284,16 +109,20 @@ fdset_init(const char *name)
> rte_strscpy(fdset->name, name, RTE_THREAD_NAME_SIZE);
>
> pthread_mutex_init(&fdset->fd_mutex, NULL);
> - pthread_mutex_init(&fdset->fd_polling_mutex, NULL);
>
> - for (i = 0; i < MAX_FDS; i++) {
> + for (i = 0; i < (int)RTE_DIM(fdset->fd); i++) {
> fdset->fd[i].fd = -1;
> fdset->fd[i].dat = NULL;
> }
> - fdset->num = 0;
> + LIST_INIT(&fdset->fdlist);
>
> - if (fdset_pipe_init(fdset)) {
> - VHOST_FDMAN_LOG(ERR, "Failed to init pipe for %s", name);
> + /*
> + * Any non-zero value would work (see man epoll_create),
> + * but pass MAX_FDS for consistency.
> + */
> + fdset->epfd = epoll_create(MAX_FDS);
> + if (fdset->epfd < 0) {
> + VHOST_FDMAN_LOG(ERR, "failed to create epoll for %s fdset", name);
failed -> Failed like other logs
> goto err_free;
> }
>
> @@ -301,7 +130,7 @@ fdset_init(const char *name)
> fdset_event_dispatch, fdset)) {
> VHOST_FDMAN_LOG(ERR, "Failed to create %s event dispatch thread",
> fdset->name);
> - goto err_pipe;
> + goto err_epoll;
> }
>
> if (fdset_insert(fdset)) {
> @@ -315,10 +144,9 @@ fdset_init(const char *name)
>
> err_thread:
> fdset->destroy = true;
> - fdset_sync(fdset);
> rte_thread_join(fdset->tid, &val);
> -err_pipe:
> - fdset_pipe_uninit(fdset);
> +err_epoll:
> + close(fdset->epfd);
> err_free:
> rte_free(fdset);
> err_unlock:
> @@ -330,78 +158,99 @@ fdset_init(const char *name)
> /**
> * Register the fd in the fdset with read/write handler and context.
> */
> -static int
> -fdset_add_no_sync(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
> +int
> +fdset_add(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
> {
> - int i;
> + struct fdentry *pfdentry;
> + struct epoll_event ev;
>
> if (pfdset == NULL || fd == -1)
> return -1;
>
> pthread_mutex_lock(&pfdset->fd_mutex);
> - i = pfdset->num < MAX_FDS ? pfdset->num++ : -1;
> - if (i == -1) {
> - pthread_mutex_lock(&pfdset->fd_polling_mutex);
> - fdset_shrink_nolock(pfdset);
> - pthread_mutex_unlock(&pfdset->fd_polling_mutex);
> - i = pfdset->num < MAX_FDS ? pfdset->num++ : -1;
> - if (i == -1) {
> - pthread_mutex_unlock(&pfdset->fd_mutex);
> - return -2;
> - }
> + if (pfdset->next_free_idx >= (int)RTE_DIM(pfdset->fd)) {
> + pthread_mutex_unlock(&pfdset->fd_mutex);
> + return -2;
> }
>
> - fdset_add_fd(pfdset, i, fd, rcb, wcb, dat);
> + pfdentry = &pfdset->fd[pfdset->next_free_idx];
> + pfdentry->fd = fd;
> + pfdentry->rcb = rcb;
> + pfdentry->wcb = wcb;
> + pfdentry->dat = dat;
> +
> + LIST_INSERT_HEAD(&pfdset->fdlist, pfdentry, next);
> +
> + /* Find next free slot */
> + pfdset->next_free_idx++;
> + for (; pfdset->next_free_idx < (int)RTE_DIM(pfdset->fd); pfdset->next_free_idx++) {
> + if (pfdset->fd[pfdset->next_free_idx].fd != -1)
> + continue;
> + break;
> + }
> pthread_mutex_unlock(&pfdset->fd_mutex);
>
> + ev.events = EPOLLERR;
> + ev.events |= rcb ? EPOLLIN : 0;
> + ev.events |= wcb ? EPOLLOUT : 0;
> + ev.data.fd = fd;
> +
> + if (epoll_ctl(pfdset->epfd, EPOLL_CTL_ADD, fd, &ev) == -1)
> + VHOST_FDMAN_LOG(ERR, "could not add %d fd to %d epfd: %s",
> + fd, pfdset->epfd, strerror(errno));
Should not return 0 if this fails ?
> +
> return 0;
> }
>
> -int
> -fdset_add(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
> +static struct fdentry *
> +fdset_find_entry_locked(struct fdset *pfdset, int fd)
> {
> - int ret;
> + struct fdentry *pfdentry;
>
> - ret = fdset_add_no_sync(pfdset, fd, rcb, wcb, dat);
> - if (ret < 0)
> - return ret;
> + LIST_FOREACH(pfdentry, &pfdset->fdlist, next) {
> + if (pfdentry->fd != fd)
> + continue;
> + return pfdentry;
> + }
>
> - fdset_sync(pfdset);
> + return NULL;
> +}
>
> - return 0;
> +static void
> +fdset_del_locked(struct fdset *pfdset, struct fdentry *pfdentry)
> +{
> + int entry_idx;
> +
> + if (epoll_ctl(pfdset->epfd, EPOLL_CTL_DEL, pfdentry->fd, NULL) == -1)
> + VHOST_FDMAN_LOG(ERR, "could not remove %d fd from %d epfd: %s",
> + pfdentry->fd, pfdset->epfd, strerror(errno));
> +
> + pfdentry->fd = -1;
> + pfdentry->rcb = pfdentry->wcb = NULL;
> + pfdentry->dat = NULL;
> + entry_idx = pfdentry - pfdset->fd;
> + if (entry_idx < pfdset->next_free_idx)
> + pfdset->next_free_idx = entry_idx;
> + LIST_REMOVE(pfdentry, next);
> }
>
> -/**
> - * Unregister the fd from the fdset.
> - * Returns context of a given fd or NULL.
> - */
> -void *
> +void
> fdset_del(struct fdset *pfdset, int fd)
> {
> - int i;
> - void *dat = NULL;
> + struct fdentry *pfdentry;
>
> if (pfdset == NULL || fd == -1)
> - return NULL;
> + return;
>
> do {
> pthread_mutex_lock(&pfdset->fd_mutex);
> -
> - i = fdset_find_fd(pfdset, fd);
> - if (i != -1 && pfdset->fd[i].busy == 0) {
> - /* busy indicates r/wcb is executing! */
> - dat = pfdset->fd[i].dat;
> - pfdset->fd[i].fd = -1;
> - pfdset->fd[i].rcb = pfdset->fd[i].wcb = NULL;
> - pfdset->fd[i].dat = NULL;
> - i = -1;
> + pfdentry = fdset_find_entry_locked(pfdset, fd);
> + if (pfdentry != NULL && pfdentry->busy == 0) {
> + fdset_del_locked(pfdset, pfdentry);
> + pfdentry = NULL;
> }
> pthread_mutex_unlock(&pfdset->fd_mutex);
> - } while (i != -1);
> -
> - fdset_sync(pfdset);
> -
> - return dat;
> + } while (pfdentry != NULL);
> }
>
> /**
> @@ -415,28 +264,22 @@ fdset_del(struct fdset *pfdset, int fd)
> int
> fdset_try_del(struct fdset *pfdset, int fd)
> {
> - int i;
> + struct fdentry *pfdentry;
>
> if (pfdset == NULL || fd == -1)
> return -2;
>
> pthread_mutex_lock(&pfdset->fd_mutex);
> - i = fdset_find_fd(pfdset, fd);
> - if (i != -1 && pfdset->fd[i].busy) {
> + pfdentry = fdset_find_entry_locked(pfdset, fd);
> + if (pfdentry != NULL && pfdentry->busy != 0) {
> pthread_mutex_unlock(&pfdset->fd_mutex);
> return -1;
> }
>
> - if (i != -1) {
> - pfdset->fd[i].fd = -1;
> - pfdset->fd[i].rcb = pfdset->fd[i].wcb = NULL;
> - pfdset->fd[i].dat = NULL;
> - }
> + if (pfdentry != NULL)
> + fdset_del_locked(pfdset, pfdentry);
>
> pthread_mutex_unlock(&pfdset->fd_mutex);
> -
> - fdset_sync(pfdset);
> -
> return 0;
> }
>
> @@ -453,53 +296,29 @@ static uint32_t
> fdset_event_dispatch(void *arg)
> {
> int i;
> - struct pollfd *pfd;
> - struct fdentry *pfdentry;
> fd_cb rcb, wcb;
> void *dat;
> int fd, numfds;
> int remove1, remove2;
> - int need_shrink;
> struct fdset *pfdset = arg;
> - int val;
>
> if (pfdset == NULL)
> return 0;
>
> while (1) {
> + struct epoll_event events[MAX_FDS];
> + struct fdentry *pfdentry;
>
> - /*
> - * When poll is blocked, other threads might unregister
> - * listenfds from and register new listenfds into fdset.
> - * When poll returns, the entries for listenfds in the fdset
> - * might have been updated. It is ok if there is unwanted call
> - * for new listenfds.
> - */
> - pthread_mutex_lock(&pfdset->fd_mutex);
> - numfds = pfdset->num;
> - pthread_mutex_unlock(&pfdset->fd_mutex);
> -
> - pthread_mutex_lock(&pfdset->fd_polling_mutex);
> - val = poll(pfdset->rwfds, numfds, 1000 /* millisecs */);
> - pthread_mutex_unlock(&pfdset->fd_polling_mutex);
> - if (val < 0)
> + numfds = epoll_wait(pfdset->epfd, events, RTE_DIM(events), 1000);
> + if (numfds < 0)
> continue;
>
> - need_shrink = 0;
> for (i = 0; i < numfds; i++) {
> pthread_mutex_lock(&pfdset->fd_mutex);
>
> - pfdentry = &pfdset->fd[i];
> - fd = pfdentry->fd;
> - pfd = &pfdset->rwfds[i];
> -
> - if (fd < 0) {
> - need_shrink = 1;
> - pthread_mutex_unlock(&pfdset->fd_mutex);
> - continue;
> - }
> -
> - if (!pfd->revents) {
> + fd = events[i].data.fd;
> + pfdentry = fdset_find_entry_locked(pfdset, fd);
> + if (pfdentry == NULL) {
> pthread_mutex_unlock(&pfdset->fd_mutex);
> continue;
> }
> @@ -513,9 +332,9 @@ fdset_event_dispatch(void *arg)
>
> pthread_mutex_unlock(&pfdset->fd_mutex);
>
> - if (rcb && pfd->revents & (POLLIN | FDPOLLERR))
> + if (rcb && events[i].events & (EPOLLIN | EPOLLERR | EPOLLHUP))
> rcb(fd, dat, &remove1);
> - if (wcb && pfd->revents & (POLLOUT | FDPOLLERR))
> + if (wcb && events[i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP))
> wcb(fd, dat, &remove2);
> pfdentry->busy = 0;
> /*
> @@ -524,23 +343,13 @@ fdset_event_dispatch(void *arg)
> * directly.
> */
> /*
> - * When we are to clean up the fd from fdset,
> - * because the fd is closed in the cb,
> - * the old fd val could be reused by when creates new
> - * listen fd in another thread, we couldn't call
> - * fdset_del.
> + * A concurrent fdset_del may have been waiting for the
> + * fdentry not to be busy, so we can't call
> + * fdset_del_locked().
> */
> - if (remove1 || remove2) {
> - pfdentry->fd = -1;
> - need_shrink = 1;
> - }
> + if (remove1 || remove2)
> + fdset_del(pfdset, fd);
> }
> -
> - if (need_shrink)
> - fdset_shrink(pfdset);
> -
> - if (pfdset->destroy)
> - break;
I guess we want to keep the destroy logic
Thanks,
Chenbo
> }
>
> return 0;
> diff --git a/lib/vhost/fd_man.h b/lib/vhost/fd_man.h
> index 079fa0155f..6398343a6a 100644
> --- a/lib/vhost/fd_man.h
> +++ b/lib/vhost/fd_man.h
> @@ -6,7 +6,7 @@
> #define _FD_MAN_H_
> #include <pthread.h>
> #include <poll.h>
> -#include <stdbool.h>
> +#include <sys/queue.h>
>
> struct fdset;
>
> @@ -19,8 +19,7 @@ struct fdset *fdset_init(const char *name);
> int fdset_add(struct fdset *pfdset, int fd,
> fd_cb rcb, fd_cb wcb, void *dat);
>
> -void *fdset_del(struct fdset *pfdset, int fd);
> -
> +void fdset_del(struct fdset *pfdset, int fd);
> int fdset_try_del(struct fdset *pfdset, int fd);
>
> #endif
> --
> 2.44.0
>
prev parent reply other threads:[~2024-04-28 3:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 11:48 [PATCH v3 0/5] vhost: FD manager improvements Maxime Coquelin
2024-04-09 11:48 ` [PATCH v3 1/5] vhost: rename polling mutex Maxime Coquelin
2024-04-09 11:48 ` [PATCH v3 2/5] vhost: make use of FD manager init function Maxime Coquelin
2024-04-09 16:38 ` Stephen Hemminger
2024-04-10 6:22 ` Maxime Coquelin
2024-04-09 11:48 ` [PATCH v3 3/5] vhost: hide synchronization within FD manager Maxime Coquelin
2024-04-09 11:48 ` [PATCH v3 4/5] vhost: improve fdset initialization Maxime Coquelin
2024-04-26 7:40 ` Chenbo Xia
2024-04-26 7:46 ` Maxime Coquelin
2024-04-09 11:48 ` [PATCH v3 5/5] vhost: manage FD with epoll Maxime Coquelin
2024-04-28 3:22 ` Chenbo Xia [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=B677E726-2C99-4734-9363-2A2D1C09611E@nvidia.com \
--to=chenbox@nvidia.com \
--cc=david.marchand@redhat.com \
--cc=dev@dpdk.org \
--cc=maxime.coquelin@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).