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port the epoll optimizations to kqueue, hopefully repairing it in the process

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leitner 2020-05-15 11:42:53 +00:00
parent 9d51f000ef
commit 69c9d1454d
1 changed files with 77 additions and 15 deletions
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92
io/io_waituntil2.c
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@ -261,27 +261,89 @@ int64 io_waituntil2(int64 milliseconds) {
for (i=n-1; i>=0; --i) {
io_entry* e=iarray_get(&io_fds,y[--n].ident);
if (e) {
/* copies from epoll above */
int curevents=0,newevents;
if (e->kernelwantread) curevents |= EVFILT_READ;
if (e->kernelwantwrite) curevents |= EVFILT_WRITE;
newevents=0;
if (!e->canread || e->wantread) {
newevents |= EVFILT_READ;
e->kernelwantread=1;
} else
e->kernelwantread=0;
if (!e->canwrite || e->wantwrite) {
newevents |= EVFILT_WRITE;
e->kernelwantwrite=1;
} else
e->kernelwantwrite=0;
if (y[n].flags&EV_ERROR) {
/* error; signal whatever app is looking for */
if (e->wantread) y[n].filter=EVFILT_READ; else
if (e->wantread) y[n].filter=EVFILT_READ;
if (e->wantwrite) y[n].filter=EVFILT_WRITE;
}
if (!e->canread && (y[n].filter==EVFILT_READ)) {
e->canread=1;
#ifdef DEBUG
assert(e->next_read==-1);
#endif
e->next_read=first_readable;
first_readable=y[n].ident;
/* if we think we can not read, but the kernel tells us that we
* can, put this fd in the relevant data structures */
if (!e->canread && (y[n].filter&EVFILT_WRITE)) {
if (e->canread) {
newevents &= ~EVFILT_READ;
} else {
e->canread=1;
if (e->wantread) {
e->next_read=first_readable;
first_readable=y[n].ident;
}
}
}
if (y[n].filter==EVFILT_WRITE) {
e->canwrite=1;
#ifdef DEBUG
assert(e->next_write==-1);
#endif
e->next_write=first_writeable;
first_writeable=y[i].ident;
/* if the kernel says the fd is writable, ... */
if (y[i].filter&EVFILT_WRITE) {
/* Usually, if the kernel says a descriptor is writable, we
* note it and do not tell the kernel not to tell us again.
* The idea is that once we notify the caller that the fd is
* writable, and the caller handles the event, the caller will
* just ask to be notified of future write events again. We
* are trying to save the superfluous epoll_ctl syscalls.
* If e->canwrite is set, then this gamble did not work out.
* We told the caller, yet after the caller is done we still
* got another write event. Clearly the user is implementing
* some kind of throttling and we can tell the kernel to leave
* us alone for now. */
if (e->canwrite) {
newevents &= ~EVFILT_WRITE;
e->kernelwantwrite=0;
} else {
/* If !e->wantwrite: The laziness optimization in
* io_dontwantwrite hit. We did not tell the kernel that we
* are no longer interested in writing to save the syscall.
* Now we know we could write if we wanted; remember that
* and then go on. */
e->canwrite=1;
if (e->wantwrite) {
e->next_write=first_writeable;
first_writeable=y[n].ident;
}
}
}
if (newevents != curevents) {
struct kevent kev;
struct timespec ts;
ts.tv_sec=0; ts.tv_nsec=0;
if (curevents &~ newevents) {
EV_SET(&kev, n, curevents &~ newevents, EV_DELETE, 0, 0, 0);
kevent(io_master,&kev,1,0,0,&ts);
}
if (newevents &~ curevents) {
EV_SET(&kev, n, newevents, EV_ADD|EV_ENABLE, 0, 0, 0);
kevent(io_master,&kev,1,0,0,&ts);
}
if (!newevents)
--io_wanted_fds;
}
#ifdef DEBUG
} else {
fprintf(stderr,"got kevent on fd#%d, which is not in array!\n",y[n].ident);