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Optimize and simplify the epoll poller 

On my own machine (4096 max FD's), scanning localhost for all services,
there was no change to speak of.  On another one, though, with 65536
max FD's scanning localhost and another machine simultaneously for
a specific service, there was a dramatic speedup allowing much faster
scans, with userspace load dropping to about a quarter of a second.

As a bonus, it makes the code simpler.
This commit is contained in:
Přemysl Eric Janouch 2014-09-24 21:39:17 +02:00
parent 49e7f1798e
commit 0e51b37411
1 changed files with 14 additions and 27 deletions
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41
utils.c
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@ -1063,11 +1063,7 @@ struct poller
struct poller_timers timers; ///< Timeouts struct poller_timers timers; ///< Timeouts
struct poller_idle *idle; ///< Idle events struct poller_idle *idle; ///< Idle events
/// Index of the element in `revents' that's about to be dispatched next. int revents_len; ///< Number of entries in `revents'
int dispatch_next;
/// The total number of entries stored in `revents' by epoll_wait().
int dispatch_total;
}; };
static void static void
@ -1081,11 +1077,9 @@ poller_init (struct poller *self)
self->alloc = POLLER_MIN_ALLOC; self->alloc = POLLER_MIN_ALLOC;
self->fds = xcalloc (self->alloc, sizeof *self->fds); self->fds = xcalloc (self->alloc, sizeof *self->fds);
self->revents = xcalloc (self->alloc, sizeof *self->revents); self->revents = xcalloc (self->alloc, sizeof *self->revents);
self->revents_len = 0;
poller_timers_init (&self->timers); poller_timers_init (&self->timers);
self->dispatch_next = 0;
self->dispatch_total = 0;
} }
static void static void
@ -1174,18 +1168,13 @@ poller_compare_fds (const void *ax, const void *bx)
static void static void
poller_remove_from_dispatch (struct poller *self, const struct poller_fd *fd) poller_remove_from_dispatch (struct poller *self, const struct poller_fd *fd)
{ {
if (!self->dispatch_total) if (!self->revents_len)
return; return;
struct epoll_event key = { .data.ptr = (void *) fd }, *fd_event; struct epoll_event key = { .data.ptr = (void *) fd }, *fd_event;
if (!(fd_event = bsearch (&key, self->revents, if ((fd_event = bsearch (&key, self->revents,
self->dispatch_total, sizeof *self->revents, poller_compare_fds))) self->revents_len, sizeof *self->revents, poller_compare_fds)))
return; fd_event->events = -1;
ssize_t i = fd_event - self->revents;
if (i < self->dispatch_next)
self->dispatch_next--;
memmove (fd_event, fd_event + 1, (--self->dispatch_total - i) * sizeof key);
} }
static void static void
@ -1211,7 +1200,7 @@ static void
poller_run (struct poller *self) poller_run (struct poller *self)
{ {
// Not reentrant // Not reentrant
hard_assert (!self->dispatch_total); hard_assert (!self->revents_len);
int n_fds; int n_fds;
do do
@ -1222,31 +1211,29 @@ poller_run (struct poller *self)
if (n_fds == -1) if (n_fds == -1)
exit_fatal ("%s: %s", "epoll", strerror (errno)); exit_fatal ("%s: %s", "epoll", strerror (errno));
self->dispatch_next = 0;
self->dispatch_total = n_fds;
// Sort them by file descriptor number for binary search // Sort them by file descriptor number for binary search
qsort (self->revents, n_fds, sizeof *self->revents, poller_compare_fds); qsort (self->revents, n_fds, sizeof *self->revents, poller_compare_fds);
self->revents_len = n_fds;
poller_timers_dispatch (&self->timers); poller_timers_dispatch (&self->timers);
poller_idle_dispatch (self->idle); poller_idle_dispatch (self->idle);
while (self->dispatch_next < self->dispatch_total) for (int i = 0; i < n_fds; i++)
{ {
struct epoll_event *revents = self->revents + self->dispatch_next; struct epoll_event *revents = self->revents + i;
struct poller_fd *fd = revents->data.ptr; if (revents->events == (uint32_t) -1)
continue;
struct poller_fd *fd = revents->data.ptr;
struct pollfd pfd; struct pollfd pfd;
pfd.fd = fd->fd; pfd.fd = fd->fd;
pfd.revents = poller_epoll_to_poll_events (revents->events); pfd.revents = poller_epoll_to_poll_events (revents->events);
pfd.events = fd->events; pfd.events = fd->events;
self->dispatch_next++;
fd->dispatcher (&pfd, fd->user_data); fd->dispatcher (&pfd, fd->user_data);
} }
self->dispatch_next = 0; self->revents_len = 0;
self->dispatch_total = 0;
} }
#else // !__linux__ #else // !__linux__