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Activate fd events in a pseudorandom order on older backends.

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New backends like poll and kqueue and so on add fds to the queue in
the order that they are triggered.  But the select backend currently
activates low-numbered fds first, whereas the poll and win32 backends
currently favor whatever fds have been on for the longest.  This is no
good for fairness.

svn:r1327
This commit is contained in:
Nick Mathewson 2009-06-24 22:39:03 +00:00
parent b0d88e680b
commit b99254ac22
4 changed files with 46 additions and 28 deletions
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2
ChangeLog
View File

@ -2,6 +2,7 @@ Changes in 1.4.12-stable:
o Try to contain degree of failure when running on a win32 version so heavily firewalled that we can't fake a socketpair.
o Fix an obscure timing-dependent, allocator-dependent crash in the evdns code.
o Use __VA_ARGS__ syntax for varargs macros in event_rpcgen when compiler is not GCC.
o Activate fd events in a pseudorandom order with O(N) backends, so that we don't systematically favor low fds (select) or earlier-added fds (poll, win32).
o Fix another pair of fencepost bugs in epoll.c. [Patch from Adam Langley.]
Changes in 1.4.11-stable:
@ -86,7 +87,6 @@ Changes in 1.4.4-stable:
o Fix autoconf script behavior on IRIX.
o Make sure winsock2.h include always comes before windows.h include.
Changes in 1.4.3-stable:
o include Content-Length in reply for HTTP/1.0 requests with keep-alive
o Patch from Tani Hosokawa: make some functions in http.c threadsafe.

51
WIN32-Code/win32.c
View File

@ -352,8 +352,9 @@ win32_dispatch(struct event_base *base, void *op,
{
struct win32op *win32op = op;
int res = 0;
unsigned i;
unsigned j, i;
int fd_count;
SOCKET s;
fd_set_copy(win32op->readset_out, win32op->readset_in);
fd_set_copy(win32op->exset_out, win32op->readset_in);
@ -384,29 +385,37 @@ win32_dispatch(struct event_base *base, void *op,
evsignal_process(base);
}
for (i=0; i<win32op->readset_out->fd_count; ++i) {
struct event_entry *ent;
SOCKET s = win32op->readset_out->fd_array[i];
if ((ent = get_event_entry(win32op, s, 0)) && ent->read_event)
event_active(ent->read_event, EV_READ, 1);
if (win32op->readset_out->fd_count) {
i = rand() % win32op->readset_out->fd_count;
for (j=0; j<win32op->readset_out->fd_count; ++j) {
if (++i >= win32op->readset_out->fd_count)
i = 0;
s = win32op->readset_out->fd_array[i];
if ((ent = get_event_entry(win32op, s, 0)) && ent->read_event)
event_active(ent->read_event, EV_READ, 1);
}
}
for (i=0; i<win32op->exset_out->fd_count; ++i) {
struct event_entry *ent;
SOCKET s = win32op->exset_out->fd_array[i];
if ((ent = get_event_entry(win32op, s, 0)) && ent->read_event)
event_active(ent->read_event, EV_READ, 1);
}
for (i=0; i<win32op->writeset_out->fd_count; ++i) {
struct event_entry *ent;
SOCKET s = win32op->writeset_out->fd_array[i];
if ((ent = get_event_entry(win32op, s, 0)) && ent->write_event)
event_active(ent->write_event, EV_WRITE, 1);
if (win32op->exset_out->fd_count) {
i = rand() % win32op->exset_out->fd_count;
for (j=0; j<win32op->exset_out->fd_count; ++j) {
if (++i >= win32op-exset_out->fd_count)
i = 0;
s = win32op->exset_out->fd_array[i];
if ((ent = get_event_entry(win32op, s, 0)) && ent->read_event)
event_active(ent->read_event, EV_READ, 1);
}
}
if (win32op->writeset_out->fd_count) {
i = rand() % win32op->writeset_out->fd_count;
for (j=0; j<win32op->writeset_out->fd_count; ++j) {
if (++i >= win32op-exset_out->fd_count)
i = 0;
s = win32op->writeset_out->fd_array[i];
if ((ent = get_event_entry(win32op, s, 0)) && ent->write_event)
event_active(ent->write_event, EV_WRITE, 1);
#if 0
if (signal_recalc() == -1)
return (-1);
#endif
}
}
return (0);
}

13
poll.c
View File

@ -135,7 +135,7 @@ poll_check_ok(struct pollop *pop)
static int
poll_dispatch(struct event_base *base, void *arg, struct timeval *tv)
{
int res, i, msec = -1, nfds;
int res, i, j, msec = -1, nfds;
struct pollop *pop = arg;
poll_check_ok(pop);
@ -160,12 +160,17 @@ poll_dispatch(struct event_base *base, void *arg, struct timeval *tv)
event_debug(("%s: poll reports %d", __func__, res));
if (res == 0)
if (res == 0 || nfds == 0)
return (0);
for (i = 0; i < nfds; i++) {
int what = pop->event_set[i].revents;
i = random() % nfds;
for (j = 0; j < nfds; j++) {
struct event *r_ev = NULL, *w_ev = NULL;
int what;
if (++i == nfds)
i = 0;
what = pop->event_set[i].revents;
if (!what)
continue;

8
select.c
View File

@ -137,7 +137,7 @@ check_selectop(struct selectop *sop)
static int
select_dispatch(struct event_base *base, void *arg, struct timeval *tv)
{
int res, i;
int res, i, j;
struct selectop *sop = arg;
check_selectop(sop);
@ -167,8 +167,12 @@ select_dispatch(struct event_base *base, void *arg, struct timeval *tv)
event_debug(("%s: select reports %d", __func__, res));
check_selectop(sop);
for (i = 0; i <= sop->event_fds; ++i) {
i = random() % (sop->event_fds+1);
for (j = 0; j <= sop->event_fds; ++j) {
struct event *r_ev = NULL, *w_ev = NULL;
if (++i >= sop->event_fds+1)
i = 0;
res = 0;
if (FD_ISSET(i, sop->event_readset_out)) {
r_ev = sop->event_r_by_fd[i];