Messages in this thread Patch in this message | | | Date | Wed, 19 Jan 2000 08:26:28 +0000 (GMT) | From | Tigran Aivazian <> | Subject | [patch-2.3.40-pre6] poll() with a chunk allocator. |
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Dear Alan, Bill and All,
Attached is my proposed solution to the poll() on many descriptors problem. Please consider it and let me know if there is something I can improve. I corrected the stuff that Bill noticed, except his suggestion to use linked lists (i.e. I still prefer chunk allocation)
http://www.ocston.org/~tigran/patches/pollfix.patch
It passed only basic tests - I didn't write a more comprehensive test yesterday - perhaps will do today.
Regards, Tigran
--- select.c.0 Wed Jan 19 08:09:21 2000 +++ select.c Wed Jan 19 08:05:44 2000 @@ -8,6 +8,10 @@ * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS * flag set in its personality we do *not* modify the given timeout * parameter to reflect time remaining. + * + * 19 January 2000 + * Changed sys_poll()/do_poll() to use chunk-based allocation of fds to + * overcome nfds < 16390 descriptors limit (Tigran Aivazian). */ #include <linux/malloc.h> @@ -328,39 +332,51 @@ return ret; } -static int do_poll(unsigned int nfds, struct pollfd *fds, poll_table *wait, +#define POLL_PER_CHUNK (1<<13) +#define POLL_PER_CHUNK_BITS (13) +#define POLL_NCHUNKS (16) + +static void do_pollfd(struct pollfd * fdp, poll_table * wait, int *count) +{ + int fd; + unsigned int mask; + + mask = 0; + fd = fdp->fd; + if (fd >= 0) { + struct file * file = fget(fd); + mask = POLLNVAL; + if (file != NULL) { + mask = DEFAULT_POLLMASK; + if (file->f_op && file->f_op->poll) + mask = file->f_op->poll(file, wait); + mask &= fdp->events | POLLERR | POLLHUP; + fput(file); + } + if (mask) { + wait = NULL; + (*count)++; + } + } + fdp->revents = mask; +} + +static int do_poll(unsigned int nfds, unsigned int nchunks, unsigned int nleft, struct pollfd *fds[], poll_table *wait, long timeout) { int count = 0; for (;;) { - unsigned int j; + unsigned int i, j; struct pollfd * fdpnt; set_current_state(TASK_INTERRUPTIBLE); - for (fdpnt = fds, j = 0; j < nfds; j++, fdpnt++) { - int fd; - unsigned int mask; - - mask = 0; - fd = fdpnt->fd; - if (fd >= 0) { - struct file * file = fget(fd); - mask = POLLNVAL; - if (file != NULL) { - mask = DEFAULT_POLLMASK; - if (file->f_op && file->f_op->poll) - mask = file->f_op->poll(file, wait); - mask &= fdpnt->events | POLLERR | POLLHUP; - fput(file); - } - if (mask) { - wait = NULL; - count++; - } - } - fdpnt->revents = mask; - } + for (i=0; i < nchunks; i++) + for (fdpnt = fds[i], j = 0; j < POLL_PER_CHUNK; j++, fdpnt++) + do_pollfd(fdpnt, wait, &count); + if (nleft) + for (fdpnt = fds[nchunks], j = 0; j < nleft; j++, fdpnt++) + do_pollfd(fdpnt, wait, &count); wait = NULL; if (count || !timeout || signal_pending(current)) @@ -373,18 +389,17 @@ asmlinkage long sys_poll(struct pollfd * ufds, unsigned int nfds, long timeout) { - int i, fdcount, err, size; - struct pollfd * fds, *fds1; + int i, j, fdcount, err; + struct pollfd * fds[POLL_NCHUNKS]; poll_table *wait_table = NULL, *wait = NULL; + int nchunks, nleft; - lock_kernel(); /* Do a sanity check on nfds ... */ - err = -EINVAL; - if (nfds > current->files->max_fds) - goto out; + if (nfds > current->files->max_fds || nfds > POLL_PER_CHUNK*POLL_NCHUNKS) + return -EINVAL; if (timeout) { - /* Carefula about overflow in the intermediate values */ + /* Careful about overflow in the intermediate values */ if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ) timeout = (unsigned long)(timeout*HZ+999)/1000+1; else /* Negative or overflow */ @@ -402,32 +417,57 @@ wait = wait_table; } - size = nfds * sizeof(struct pollfd); - fds = (struct pollfd *) kmalloc(size, GFP_KERNEL); - if (!fds) - goto out; + nchunks = 0; + nleft = nfds; + while (nleft > POLL_PER_CHUNK) { /* allocate complete chunks */ + fds[nchunks] = kmalloc(POLL_PER_CHUNK * sizeof(struct pollfd), GFP_KERNEL); + if (fds[nchunks] == NULL) + goto out_fds; + nchunks++; + nleft -= POLL_PER_CHUNK; + } + if (nleft) { /* allocate last chunk, incomplete = nleft elements */ + fds[nchunks] = kmalloc(nleft * sizeof(struct pollfd), GFP_KERNEL); + if (fds[nchunks] == NULL) + goto out_fds; + } err = -EFAULT; - if (copy_from_user(fds, ufds, size)) - goto out_fds; + for (i=0; i < nchunks; i++) { + if (copy_from_user(fds[i], ufds + (i<<POLL_PER_CHUNK_BITS), + POLL_PER_CHUNK * sizeof(struct pollfd))) + goto out_fds1; + } + if (nleft) { + if (copy_from_user(fds[nchunks], ufds + (nchunks<<POLL_PER_CHUNK_BITS), + nleft * sizeof(struct pollfd))) + goto out_fds1; + } - fdcount = do_poll(nfds, fds, wait, timeout); + lock_kernel(); + fdcount = do_poll(nfds, nchunks, nleft, fds, wait, timeout); + unlock_kernel(); /* OK, now copy the revents fields back to user space. */ - fds1 = fds; - for(i=0; i < (int)nfds; i++, ufds++, fds1++) { - __put_user(fds1->revents, &ufds->revents); + for(i=0; i < nchunks; i++) { + struct pollfd *u; + u = ufds + (i<<POLL_PER_CHUNK_BITS); + for (j=0; j < POLL_PER_CHUNK; j++) + __put_user((fds[i] + j)->revents, &u->revents); } err = fdcount; if (!fdcount && signal_pending(current)) err = -EINTR; +out_fds1: + if (nleft) + kfree(fds[nchunks]); out_fds: - kfree(fds); + for (i=0; i < nchunks; i++) + kfree(fds[i]); out: if (wait) free_wait(wait_table); - unlock_kernel(); return err; }
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