MEDIUM: polling: start to move maxfd computation to the pollers
Since only select() and poll() still make use of maxfd, let's move
its computation right there in the pollers themselves, and only
during each fd update pass. The computation doesn't need a lock
anymore, only a few atomic ops. It will be accurate, be done much
less often and will not be required anymore in the FD's fast patch.
This provides a small performance increase of about 1% in connection
rate when using epoll since we get rid of this computation which was
performed under a lock.
diff --git a/src/ev_poll.c b/src/ev_poll.c
index f24bf69..2e67a9d 100644
--- a/src/ev_poll.c
+++ b/src/ev_poll.c
@@ -32,6 +32,7 @@
#define POLLRDHUP 0
#endif
+static int maxfd; /* # of the highest fd + 1 */
static unsigned int *fd_evts[2];
/* private data */
@@ -67,8 +68,11 @@
int updt_idx, en, eo;
int fds, count;
int sr, sw;
+ int old_maxfd, new_maxfd, max_add_fd;
unsigned rn, wn; /* read new, write new */
+ max_add_fd = -1;
+
/* first, scan the update list to find changes */
for (updt_idx = 0; updt_idx < fd_nbupdt; updt_idx++) {
fd = fd_updt[updt_idx];
@@ -100,8 +104,32 @@
else if ((en & ~eo) & FD_EV_POLLED_W)
hap_fd_set(fd, fd_evts[DIR_WR]);
HA_SPIN_UNLOCK(POLL_LOCK, &poll_lock);
+
+ if (fd > max_add_fd)
+ max_add_fd = fd;
}
}
+
+ /* maybe we added at least one fd larger than maxfd */
+ for (old_maxfd = maxfd; old_maxfd <= max_add_fd; ) {
+ if (HA_ATOMIC_CAS(&maxfd, &old_maxfd, max_add_fd + 1))
+ break;
+ }
+
+ /* maxfd doesn't need to be precise but it needs to cover *all* active
+ * FDs. Thus we only shrink it if we have such an opportunity. The algo
+ * is simple : look for the previous used place, try to update maxfd to
+ * point to it, abort if maxfd changed in the mean time.
+ */
+ old_maxfd = maxfd;
+ do {
+ new_maxfd = old_maxfd;
+ while (new_maxfd - 1 >= 0 && !fdtab[new_maxfd - 1].owner)
+ new_maxfd--;
+ if (new_maxfd >= old_maxfd)
+ break;
+ } while (!HA_ATOMIC_CAS(&maxfd, &old_maxfd, new_maxfd));
+
fd_nbupdt = 0;
nbfd = 0;
diff --git a/src/ev_select.c b/src/ev_select.c
index 19b1380..9d53a85 100644
--- a/src/ev_select.c
+++ b/src/ev_select.c
@@ -25,6 +25,7 @@
/* private data */
+static int maxfd; /* # of the highest fd + 1 */
static fd_set *fd_evts[2];
static THREAD_LOCAL fd_set *tmp_evts[2];
@@ -50,6 +51,9 @@
int updt_idx, en, eo;
char count;
int readnotnull, writenotnull;
+ int old_maxfd, new_maxfd, max_add_fd;
+
+ max_add_fd = -1;
/* first, scan the update list to find changes */
for (updt_idx = 0; updt_idx < fd_nbupdt; updt_idx++) {
@@ -74,16 +78,44 @@
HA_SPIN_LOCK(POLL_LOCK, &poll_lock);
if ((eo & ~en) & FD_EV_POLLED_R)
FD_CLR(fd, fd_evts[DIR_RD]);
- else if ((en & ~eo) & FD_EV_POLLED_R)
+ else if ((en & ~eo) & FD_EV_POLLED_R) {
FD_SET(fd, fd_evts[DIR_RD]);
+ if (fd > max_add_fd)
+ max_add_fd = fd;
+ }
if ((eo & ~en) & FD_EV_POLLED_W)
FD_CLR(fd, fd_evts[DIR_WR]);
- else if ((en & ~eo) & FD_EV_POLLED_W)
+ else if ((en & ~eo) & FD_EV_POLLED_W) {
FD_SET(fd, fd_evts[DIR_WR]);
+ if (fd > max_add_fd)
+ max_add_fd = fd;
+ }
+
HA_SPIN_UNLOCK(POLL_LOCK, &poll_lock);
}
}
+
+ /* maybe we added at least one fd larger than maxfd */
+ for (old_maxfd = maxfd; old_maxfd <= max_add_fd; ) {
+ if (HA_ATOMIC_CAS(&maxfd, &old_maxfd, max_add_fd + 1))
+ break;
+ }
+
+ /* maxfd doesn't need to be precise but it needs to cover *all* active
+ * FDs. Thus we only shrink it if we have such an opportunity. The algo
+ * is simple : look for the previous used place, try to update maxfd to
+ * point to it, abort if maxfd changed in the mean time.
+ */
+ old_maxfd = maxfd;
+ do {
+ new_maxfd = old_maxfd;
+ while (new_maxfd - 1 >= 0 && !fdtab[new_maxfd - 1].owner)
+ new_maxfd--;
+ if (new_maxfd >= old_maxfd)
+ break;
+ } while (!HA_ATOMIC_CAS(&maxfd, &old_maxfd, new_maxfd));
+
fd_nbupdt = 0;
/* let's restore fdset state */
diff --git a/src/fd.c b/src/fd.c
index 4397f6e..1fa170b 100644
--- a/src/fd.c
+++ b/src/fd.c
@@ -160,7 +160,6 @@
struct fdtab *fdtab = NULL; /* array of all the file descriptors */
struct fdinfo *fdinfo = NULL; /* less-often used infos for file descriptors */
-int maxfd; /* # of the highest fd + 1 */
int totalconn; /* total # of terminated sessions */
int actconn; /* # of active sessions */
@@ -179,7 +178,7 @@
__decl_hathreads(HA_RWLOCK_T fdcache_lock); /* global lock to protect fd_cache array */
__decl_hathreads(HA_SPINLOCK_T poll_lock); /* global lock to protect poll info */
-/* Deletes an FD from the fdsets, and recomputes the maxfd limit.
+/* Deletes an FD from the fdsets.
* The file descriptor is also closed.
*/
static void fd_dodelete(int fd, int do_close)
@@ -207,14 +206,9 @@
close(fd);
}
HA_SPIN_UNLOCK(FD_LOCK, &fdtab[fd].lock);
-
- HA_SPIN_LOCK(FDTAB_LOCK, &fdtab_lock);
- while ((maxfd-1 >= 0) && !fdtab[maxfd-1].owner)
- maxfd--;
- HA_SPIN_UNLOCK(FDTAB_LOCK, &fdtab_lock);
}
-/* Deletes an FD from the fdsets, and recomputes the maxfd limit.
+/* Deletes an FD from the fdsets.
* The file descriptor is also closed.
*/
void fd_delete(int fd)
@@ -222,7 +216,7 @@
fd_dodelete(fd, 1);
}
-/* Deletes an FD from the fdsets, and recomputes the maxfd limit.
+/* Deletes an FD from the fdsets.
* The file descriptor is kept open.
*/
void fd_remove(int fd)
diff --git a/src/haproxy.c b/src/haproxy.c
index 34e8f75..11849fe 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1298,7 +1298,7 @@
* Initialize the previously static variables.
*/
- totalconn = actconn = maxfd = listeners = stopping = 0;
+ totalconn = actconn = listeners = stopping = 0;
killed = 0;