[MAJOR] ev_epoll: do not rely on fd_sets anymore
The new epoll-based poller uses a list of changes in order to
process only the fds which have changed.
diff --git a/src/ev_epoll.c b/src/ev_epoll.c
index e37fe0d..89315ea 100644
--- a/src/ev_epoll.c
+++ b/src/ev_epoll.c
@@ -16,6 +16,7 @@
#include <common/compat.h>
#include <common/config.h>
+#include <common/standard.h>
#include <common/time.h>
#include <types/fd.h>
@@ -35,67 +36,185 @@
#include <sys/epoll.h>
#endif
+/* This is what we store in a list. It consists in old values and fds to detect changes. */
+struct fd_chg {
+ unsigned int prev:2; // previous state mask. New one is in fd_evts.
+ unsigned int fd:30; // file descriptor
+};
-static fd_set *fd_evts[2];
-static fd_set *old_evts[2];
+static int nbchanges = 0; // number of changes pending
+static struct fd_chg *chg_list = NULL; // list of changes
+static struct fd_chg **chg_ptr = NULL; // per-fd changes
+
+/* Each 32-bit word contains 2-bit descriptors of the latest state for 16 FDs :
+ * desc = (u32 >> (2*fd)) & 3
+ * desc = 0 : FD not set
+ * 1 : WRITE not set, READ set
+ * 2 : WRITE set, READ not set
+ * 3 : WRITE set, READ set
+ */
+
+static uint32_t *fd_evts;
/* private data */
static struct epoll_event *epoll_events;
static int epoll_fd;
+/* This structure may be used for any purpose. Warning! do not use it in
+ * recursive functions !
+ */
+static struct epoll_event ev;
+
+/* converts a direction to a single bitmask.
+ * 0 => 1
+ * 1 => 2
+ */
+#define DIR2MSK(dir) ((dir) + 1)
+
+/* converts an FD to an fd_evts offset and to a bit shift */
+#define FD2OFS(fd) ((uint32_t)(fd) >> 4)
+#define FD2BIT(fd) (((uint32_t)(fd) & 0xF) << 1)
+#define FD2MSK(fd) (3 << FD2BIT(fd))
/*
- * Benchmarks performed on a Pentium-M notebook show that using functions
- * instead of the usual macros improve the FD_* performance by about 80%,
- * and that marking them regparm(2) adds another 20%.
+ * Returns non-zero if direction <dir> is already set for <fd>.
*/
REGPRM2 static int __fd_is_set(const int fd, int dir)
{
- return FD_ISSET(fd, fd_evts[dir]);
+ return (fd_evts[FD2OFS(fd)] >> FD2BIT(fd)) & DIR2MSK(dir);
}
-REGPRM2 static int __fd_set(const int fd, int dir)
+/*
+ * Adds, mods or deletes <fd> according to current status and to new desired
+ * mask <dmask> :
+ *
+ * 0 = nothing
+ * 1 = EPOLLIN
+ * 2 = EPOLLOUT
+ * 3 = EPOLLIN | EPOLLOUT
+ *
+ */
+static int dmsk2event[4] = { 0, EPOLLIN, EPOLLOUT, EPOLLIN | EPOLLOUT };
+
+
+REGPRM2 static void fd_flush_changes()
{
- FD_SET(fd, fd_evts[dir]);
- return 0;
+ uint32_t ofs;
+ int opcode;
+ int prev, next;
+ int chg, fd;
+
+ for (chg = 0; chg < nbchanges; chg++) {
+ prev = chg_list[chg].prev;
+ fd = chg_list[chg].fd;
+ chg_ptr[fd] = NULL;
+
+ ofs = FD2OFS(fd);
+ next = (fd_evts[ofs] >> FD2BIT(fd)) & 3;
+
+ if (prev == next)
+ /* if the value was unchanged, do nothing */
+ continue;
+
+ ev.events = dmsk2event[next];
+ ev.data.fd = fd;
+
+ if (prev) {
+ if (!next) {
+ /* we want to delete it now */
+ opcode = EPOLL_CTL_DEL;
+ } else {
+ /* we want to switch it */
+ opcode = EPOLL_CTL_MOD;
+ }
+ } else {
+ /* the FD did not exist, let's add it */
+ opcode = EPOLL_CTL_ADD;
+ }
+
+ epoll_ctl(epoll_fd, opcode, fd, &ev);
+ }
+ nbchanges = 0;
}
-REGPRM2 static int __fd_clr(const int fd, int dir)
+REGPRM2 static void alloc_chg_list(const int fd, int old_evt)
{
- FD_CLR(fd, fd_evts[dir]);
- return 0;
+ struct fd_chg *ptr;
+
+ if (unlikely(chg_ptr[fd]))
+ return;
+
+#if LIMIT_NUMBER_OF_CHANGES
+ if (nbchanges > 2)
+ fd_flush_changes();
+#endif
+
+ ptr = &chg_list[nbchanges++];
+ chg_ptr[fd] = ptr;
+ ptr->fd = fd;
+ ptr->prev = old_evt;
}
-REGPRM2 static int __fd_cond_s(const int fd, int dir)
+REGPRM2 static int __fd_set(const int fd, int dir)
{
- int ret;
- ret = !FD_ISSET(fd, fd_evts[dir]);
- if (ret)
- FD_SET(fd, fd_evts[dir]);
- return ret;
+ uint32_t ofs = FD2OFS(fd);
+ uint32_t dmsk = DIR2MSK(dir);
+ uint32_t old_evt;
+
+ old_evt = fd_evts[ofs] >> FD2BIT(fd);
+ old_evt &= 3;
+ if (unlikely(old_evt & dmsk))
+ return 0;
+
+ alloc_chg_list(fd, old_evt);
+ dmsk <<= FD2BIT(fd);
+ fd_evts[ofs] |= dmsk;
+ return 1;
}
-REGPRM2 static int __fd_cond_c(const int fd, int dir)
+REGPRM2 static int __fd_clr(const int fd, int dir)
{
- int ret;
- ret = FD_ISSET(fd, fd_evts[dir]);
- if (ret)
- FD_CLR(fd, fd_evts[dir]);
- return ret;
+ uint32_t ofs = FD2OFS(fd);
+ uint32_t dmsk = DIR2MSK(dir);
+ uint32_t old_evt;
+
+ old_evt = fd_evts[ofs] >> FD2BIT(fd);
+ old_evt &= 3;
+ if (unlikely(!(old_evt & dmsk)))
+ return 0;
+
+ alloc_chg_list(fd, old_evt);
+ dmsk <<= FD2BIT(fd);
+ fd_evts[ofs] &= ~dmsk;
+ return 1;
}
-REGPRM1 static void __fd_rem(const int fd)
+REGPRM1 static void __fd_rem(int fd)
{
- FD_CLR(fd, fd_evts[DIR_RD]);
- FD_CLR(fd, fd_evts[DIR_WR]);
+ uint32_t ofs = FD2OFS(fd);
+
+ if (unlikely(!((fd_evts[ofs] >> FD2BIT(fd)) & 3)))
+ return;
+
+ alloc_chg_list(fd, 0);
+ fd_evts[ofs] &= ~FD2MSK(fd);
+ return;
}
-REGPRM1 static void __fd_clo(const int fd)
+/*
+ * On valid epoll() implementations, a call to close() automatically removes
+ * the fds. This means that the FD will appear as previously unset.
+ */
+REGPRM1 static void __fd_clo(int fd)
{
- FD_CLR(fd, fd_evts[DIR_RD]);
- FD_CLR(fd, fd_evts[DIR_WR]);
- FD_CLR(fd, old_evts[DIR_RD]);
- FD_CLR(fd, old_evts[DIR_WR]);
+ struct fd_chg *ptr;
+ fd_evts[FD2OFS(fd)] &= ~FD2MSK(fd);
+ ptr = chg_ptr[fd];
+ if (ptr) {
+ ptr->prev = 0;
+ chg_ptr[fd] = NULL;
+ }
+ return;
}
/*
@@ -105,93 +224,11 @@
{
int status;
int fd;
-
- int fds, count;
- int pr, pw, sr, sw;
- unsigned rn, ro, wn, wo; /* read new, read old, write new, write old */
- struct epoll_event ev;
-
- for (fds = 0; (fds << INTBITS) < maxfd; fds++) {
-
- rn = ((int*)fd_evts[DIR_RD])[fds]; ro = ((int*)old_evts[DIR_RD])[fds];
- wn = ((int*)fd_evts[DIR_WR])[fds]; wo = ((int*)old_evts[DIR_WR])[fds];
-
- if ((ro^rn) | (wo^wn)) {
- for (count = 0, fd = fds << INTBITS; count < (1<<INTBITS) && fd < maxfd; count++, fd++) {
-#define FDSETS_ARE_INT_ALIGNED
-#ifdef FDSETS_ARE_INT_ALIGNED
+ int count;
-#define WE_REALLY_NOW_THAT_FDSETS_ARE_INTS
-#ifdef WE_REALLY_NOW_THAT_FDSETS_ARE_INTS
- pr = (ro >> count) & 1;
- pw = (wo >> count) & 1;
- sr = (rn >> count) & 1;
- sw = (wn >> count) & 1;
-#else
- pr = FD_ISSET(fd&((1<<INTBITS)-1), (typeof(fd_set*))&ro);
- pw = FD_ISSET(fd&((1<<INTBITS)-1), (typeof(fd_set*))&wo);
- sr = FD_ISSET(fd&((1<<INTBITS)-1), (typeof(fd_set*))&rn);
- sw = FD_ISSET(fd&((1<<INTBITS)-1), (typeof(fd_set*))&wn);
-#endif
-#else
- pr = FD_ISSET(fd, old_evts[DIR_RD]);
- pw = FD_ISSET(fd, old_evts[DIR_WR]);
- sr = FD_ISSET(fd, fd_evts[DIR_RD]);
- sw = FD_ISSET(fd, fd_evts[DIR_WR]);
-#endif
- if (!((sr^pr) | (sw^pw)))
- continue;
+ if (likely(nbchanges))
+ fd_flush_changes();
- ev.events = (sr ? EPOLLIN : 0) | (sw ? EPOLLOUT : 0);
- ev.data.fd = fd;
-
-#ifdef EPOLL_CTL_MOD_WORKAROUND
- /* I encountered a rarely reproducible problem with
- * EPOLL_CTL_MOD where a modified FD (systematically
- * the one in epoll_events[0], fd#7) would sometimes
- * be set EPOLL_OUT while asked for a read ! This is
- * with the 2.4 epoll patch. The workaround is to
- * delete then recreate in case of modification.
- * This is in 2.4 up to epoll-lt-0.21 but not in 2.6
- * nor RHEL kernels.
- */
-
- if ((pr | pw) && fdtab[fd].state != FD_STCLOSE)
- epoll_ctl(epoll_fd, EPOLL_CTL_DEL, fd, &ev);
-
- if ((sr | sw))
- epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fd, &ev);
-#else
- if ((pr | pw)) {
- /* the file-descriptor already exists... */
- if ((sr | sw)) {
- /* ...and it will still exist */
- if (epoll_ctl(epoll_fd, EPOLL_CTL_MOD, fd, &ev) < 0) {
- // perror("epoll_ctl(MOD)");
- // exit(1);
- }
- } else {
- /* ...and it will be removed */
- if (fdtab[fd].state != FD_STCLOSE &&
- epoll_ctl(epoll_fd, EPOLL_CTL_DEL, fd, &ev) < 0) {
- // perror("epoll_ctl(DEL)");
- // exit(1);
- }
- }
- } else {
- /* the file-descriptor did not exist, let's add it */
- if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
- // perror("epoll_ctl(ADD)");
- // exit(1);
- }
- }
-#endif // EPOLL_CTL_MOD_WORKAROUND
- }
- ((int*)old_evts[DIR_RD])[fds] = rn;
- ((int*)old_evts[DIR_WR])[fds] = wn;
- }
- }
-
/* now let's wait for events */
status = epoll_wait(epoll_fd, epoll_events, maxfd, wait_time);
tv_now(&now);
@@ -199,14 +236,14 @@
for (count = 0; count < status; count++) {
fd = epoll_events[count].data.fd;
- if (FD_ISSET(fd, fd_evts[DIR_RD])) {
+ if ((fd_evts[FD2OFS(fd)] >> FD2BIT(fd)) & DIR2MSK(DIR_RD)) {
if (fdtab[fd].state == FD_STCLOSE)
continue;
if (epoll_events[count].events & ( EPOLLIN | EPOLLERR | EPOLLHUP ))
fdtab[fd].cb[DIR_RD].f(fd);
}
- if (FD_ISSET(fd, fd_evts[DIR_WR])) {
+ if ((fd_evts[FD2OFS(fd)] >> FD2BIT(fd)) & DIR2MSK(DIR_WR)) {
if (fdtab[fd].state == FD_STCLOSE)
continue;
if (epoll_events[count].events & ( EPOLLOUT | EPOLLERR | EPOLLHUP ))
@@ -222,11 +259,11 @@
*/
REGPRM1 static int epoll_init(struct poller *p)
{
- __label__ fail_pwevt, fail_prevt, fail_swevt, fail_srevt, fail_ee, fail_fd;
+ __label__ fail_chg_ptr, fail_chg_list, fail_fdevt, fail_ee, fail_fd;
int fd_set_bytes;
p->private = NULL;
- fd_set_bytes = sizeof(fd_set) * (global.maxsock + FD_SETSIZE - 1) / FD_SETSIZE;
+ fd_set_bytes = 4 * (global.maxsock + 15) / 16;
epoll_fd = epoll_create(global.maxsock + 1);
if (epoll_fd < 0)
@@ -238,27 +275,24 @@
if (epoll_events == NULL)
goto fail_ee;
- if ((old_evts[DIR_RD] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
- goto fail_prevt;
+ if ((fd_evts = (uint32_t *)calloc(1, fd_set_bytes)) == NULL)
+ goto fail_fdevt;
- if ((old_evts[DIR_WR] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
- goto fail_pwevt;
-
- if ((fd_evts[DIR_RD] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
- goto fail_srevt;
+ chg_list = (struct fd_chg *)calloc(1, sizeof(struct fd_chg) * global.maxsock);
+ if (chg_list == NULL)
+ goto fail_chg_list;
- if ((fd_evts[DIR_WR] = (fd_set *)calloc(1, fd_set_bytes)) == NULL)
- goto fail_swevt;
+ chg_ptr = (struct fd_chg **)calloc(1, sizeof(struct fd_chg*) * global.maxsock);
+ if (chg_ptr == NULL)
+ goto fail_chg_ptr;
return 1;
- fail_swevt:
- free(fd_evts[DIR_RD]);
- fail_srevt:
- free(old_evts[DIR_WR]);
- fail_pwevt:
- free(old_evts[DIR_RD]);
- fail_prevt:
+ fail_chg_ptr:
+ free(chg_list);
+ fail_chg_list:
+ free(fd_evts);
+ fail_fdevt:
free(epoll_events);
fail_ee:
close(epoll_fd);
@@ -274,24 +308,25 @@
*/
REGPRM1 static void epoll_term(struct poller *p)
{
- if (fd_evts[DIR_WR])
- free(fd_evts[DIR_WR]);
+ fd_flush_changes();
- if (fd_evts[DIR_RD])
- free(fd_evts[DIR_RD]);
-
- if (old_evts[DIR_WR])
- free(old_evts[DIR_WR]);
-
- if (old_evts[DIR_RD])
- free(old_evts[DIR_RD]);
-
+ if (chg_ptr)
+ free(chg_ptr);
+ if (chg_list)
+ free(chg_list);
+ if (fd_evts)
+ free(fd_evts);
if (epoll_events)
free(epoll_events);
close(epoll_fd);
epoll_fd = 0;
+ chg_ptr = NULL;
+ chg_list = NULL;
+ fd_evts = NULL;
+ epoll_events = NULL;
+
p->private = NULL;
p->pref = 0;
}
@@ -324,13 +359,13 @@
p->init = epoll_init;
p->term = epoll_term;
p->poll = epoll_poll;
- p->is_set = __fd_is_set;
- p->set = __fd_set;
- p->clr = __fd_clr;
+
+ p->is_set = __fd_is_set;
+ p->cond_s = p->set = __fd_set;
+ p->cond_c = p->clr = __fd_clr;
p->rem = __fd_rem;
p->clo = __fd_clo;
- p->cond_s = __fd_cond_s;
- p->cond_c = __fd_cond_c;
+
return 1;
}