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    SubjectRe: [PATCH] Additions to Manfred patch to ncpfs
    I found another minor problem:

    The old code avoided building the wait table when the timeout is 0, now we
    always build the wait table.

    Below is an update for the memory allocations within fs/select.c:

    * do not build the wait table if timeout==0
    * store the first 8 poll_table_entries within the poll_table.
    * sys_select: if select is called for <= 256 bits, then store these bits
    on the stack.
    * sys_poll: replace the arrays with a linked list, and begin that list on
    the stack (the first 24 entries).

    It means that sys_poll and sys_select both store around 450 bytes on the
    stack - IMHO acceptable.

    Result: poll() for one file descriptor: down from ~3200 cpu ticks to
    ~1000 cpu ticks.

    The patch was tested with test4-pre4.
    Petr, could you double check that I didn't break ncpfs?

    --
    Manfred

    <<<<<<<<<<
    // $Header$
    // Kernel Version:
    // VERSION = 2
    // PATCHLEVEL = 4
    // SUBLEVEL = 0
    // EXTRAVERSION = -test4
    --- 2.4/fs/select.c Wed Jul 12 20:06:25 2000
    +++ build-2.4/fs/select.c Wed Jul 12 20:54:35 2000
    @@ -40,8 +40,15 @@
    void poll_freewait(poll_table* pt)
    {
    struct poll_table_page * p = pt->table;
    + struct poll_table_entry * entry;
    + entry = pt->internal + pt->nr;
    + while(pt->nr > 0) {
    + pt->nr--;
    + entry--;
    + remove_wait_queue(entry->wait_address,&entry->wait);
    + fput(entry->filp);
    + }
    while (p) {
    - struct poll_table_entry * entry;
    struct poll_table_page *old;

    entry = p->entry + p->nr;
    @@ -53,41 +60,44 @@
    }
    old = p;
    p = p->next;
    - free_page((unsigned long) old);
    + kfree(old);
    }
    }

    void __pollwait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
    {
    - struct poll_table_page *table = p->table;
    -
    - if (!table || table->nr >= __MAX_POLL_TABLE_ENTRIES) {
    - struct poll_table_page *new_table;
    + struct poll_table_entry * entry;

    - new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
    - if (!new_table) {
    - p->error = -ENOMEM;
    - __set_current_state(TASK_RUNNING);
    - return;
    - }
    - new_table->nr = 0;
    - new_table->entry = (struct poll_table_entry *)(new_table + 1);
    - new_table->next = table;
    - p->table = new_table;
    - table = new_table;
    - }
    -
    - /* Add a new entry */
    - {
    - struct poll_table_entry * entry;
    + if(p->nr < POLL_TABLE_INTERNAL) {
    + entry = p->internal + p->nr;
    + p->nr++;
    + } else {
    + struct poll_table_page *table = p->table;
    + if (!table || table->nr >= __MAX_POLL_TABLE_ENTRIES) {
    + struct poll_table_page *new_table;
    +
    + new_table = (struct poll_table_page *) kmalloc(PAGE_SIZE,GFP_KERNEL);
    + if (!new_table) {
    + p->error = -ENOMEM;
    + __set_current_state(TASK_RUNNING);
    + return;
    + }
    + new_table->nr = 0;
    + new_table->entry = (struct poll_table_entry *)(new_table + 1);
    + new_table->next = table;
    + p->table = new_table;
    + table = new_table;
    + }
    entry = table->entry + table->nr;
    table->nr++;
    - get_file(filp);
    - entry->filp = filp;
    - entry->wait_address = wait_address;
    - init_waitqueue_entry(&entry->wait, current);
    - add_wait_queue(wait_address,&entry->wait);
    }
    +
    + /* Add a new entry */
    + get_file(filp);
    + entry->filp = filp;
    + entry->wait_address = wait_address;
    + init_waitqueue_entry(&entry->wait, current);
    + add_wait_queue(wait_address,&entry->wait);
    }

    #define __IN(fds, n) (fds->in + n)
    @@ -163,7 +173,10 @@
    n = retval;

    poll_initwait(&table);
    - wait = &table;
    + if(__timeout)
    + wait = &table;
    + else
    + wait = NULL;
    retval = 0;
    for (;;) {
    set_current_state(TASK_INTERRUPTIBLE);
    @@ -234,6 +247,7 @@
    sys_select(int n, fd_set *inp, fd_set *outp, fd_set *exp, struct timeval *tvp)
    {
    fd_set_bits fds;
    + char inline_bits[192];
    char *bits;
    long timeout;
    int ret, size;
    @@ -271,9 +285,13 @@
    */
    ret = -ENOMEM;
    size = FDS_BYTES(n);
    - bits = kmalloc(6 * size, GFP_KERNEL);
    - if (!bits)
    - goto out_nofds;
    + if(size <= sizeof(inline_bits)/6) {
    + bits = inline_bits;
    + } else {
    + bits = kmalloc(6 * size, GFP_KERNEL);
    + if (!bits)
    + goto out_nofds;
    + }
    fds.in = (unsigned long *) bits;
    fds.out = (unsigned long *) (bits + size);
    fds.ex = (unsigned long *) (bits + 2*size);
    @@ -316,12 +334,18 @@
    set_fd_set(n, exp, fds.res_ex);

    out:
    - kfree(bits);
    + if(bits != inline_bits)
    + kfree(bits);
    out_nofds:
    return ret;
    }

    -#define POLLFD_PER_PAGE ((PAGE_SIZE) / sizeof(struct pollfd))
    +struct poll_list {
    + struct poll_list *next;
    + int len;
    +};
    +
    + #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))

    static void do_pollfd(unsigned int num, struct pollfd * fdpage,
    poll_table ** pwait, int *count)
    @@ -355,38 +379,44 @@
    }
    }

    -static int do_poll(unsigned int nfds, unsigned int nchunks, unsigned int nleft,
    - struct pollfd *fds[], poll_table *wait, long timeout)
    +
    +static int do_poll(int nfds, struct poll_list *list,
    + poll_table *wait, long timeout)
    {
    int count = 0;
    poll_table* pt = wait;
    -
    +
    for (;;) {
    - unsigned int i;
    -
    + struct poll_list* walk;
    set_current_state(TASK_INTERRUPTIBLE);
    - for (i=0; i < nchunks; i++)
    - do_pollfd(POLLFD_PER_PAGE, fds[i], &pt, &count);
    - if (nleft)
    - do_pollfd(nleft, fds[nchunks], &pt, &count);
    + walk = list;
    + while(walk != NULL) {
    + do_pollfd( walk->len, (struct pollfd*)(walk+1), &pt, &count);
    + walk = walk->next;
    + }
    pt = NULL;
    if (count || !timeout || signal_pending(current))
    break;
    - if(wait->error) {
    + if(wait->error)
    return wait->error;
    - }
    +
    timeout = schedule_timeout(timeout);
    }
    current->state = TASK_RUNNING;
    return count;
    }

    +#define INLINE_POLL_COUNT 24
    asmlinkage long sys_poll(struct pollfd * ufds, unsigned int nfds, long timeout)
    {
    - int i, j, fdcount, err;
    - struct pollfd **fds;
    + int fdcount, err;
    + unsigned int i;
    + struct poll_list *pollwalk;
    + struct {
    + struct poll_list head;
    + struct pollfd entries[INLINE_POLL_COUNT];
    + } polllist;
    poll_table table;
    - int nchunks, nleft;

    /* Do a sanity check on nfds ... */
    if (nfds > current->files->max_fds)
    @@ -402,64 +432,65 @@

    poll_initwait(&table);
    err = -ENOMEM;
    -
    - fds = NULL;
    - if (nfds != 0) {
    - fds = (struct pollfd **)kmalloc(
    - (1 + (nfds - 1) / POLLFD_PER_PAGE) * sizeof(struct pollfd *),
    - GFP_KERNEL);
    - if (fds == NULL)
    - goto out;
    - }
    -
    - nchunks = 0;
    - nleft = nfds;
    - while (nleft > POLLFD_PER_PAGE) { /* allocate complete PAGE_SIZE chunks */
    - fds[nchunks] = (struct pollfd *)__get_free_page(GFP_KERNEL);
    - if (fds[nchunks] == NULL)
    + polllist.head.next = NULL;
    + if(nfds <= INLINE_POLL_COUNT)
    + polllist.head.len = nfds;
    + else
    + polllist.head.len = INLINE_POLL_COUNT;
    + pollwalk = &polllist.head;
    + i = nfds;
    + err = -ENOMEM;
    + goto start;
    + while(i!=0) {
    + struct poll_list *pp;
    + pp = kmalloc(sizeof(struct poll_list)+
    + sizeof(struct pollfd)*
    + (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
    + GFP_KERNEL);
    + if(pp==NULL)
    goto out_fds;
    - nchunks++;
    - nleft -= POLLFD_PER_PAGE;
    - }
    - if (nleft) { /* allocate last PAGE_SIZE chunk, only nleft elements used */
    - fds[nchunks] = (struct pollfd *)__get_free_page(GFP_KERNEL);
    - if (fds[nchunks] == NULL)
    + pp->next=NULL;
    + pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
    + pollwalk->next = pp;
    + pollwalk = pp;
    +start:
    + if (copy_from_user(pollwalk+1, ufds + nfds-i,
    + sizeof(struct pollfd)*pollwalk->len)) {
    + err = -EFAULT;
    goto out_fds;
    + }
    + i -= pollwalk->len;
    }
    +
    + fdcount = do_poll(nfds, &polllist.head,
    + timeout!=0?&table:NULL, timeout);

    + /* OK, now copy the revents fields back to user space. */
    + i = nfds;
    + pollwalk = &polllist.head;
    err = -EFAULT;
    - for (i=0; i < nchunks; i++)
    - if (copy_from_user(fds[i], ufds + i*POLLFD_PER_PAGE, PAGE_SIZE))
    - goto out_fds1;
    - if (nleft) {
    - if (copy_from_user(fds[nchunks], ufds + nchunks*POLLFD_PER_PAGE,
    - nleft * sizeof(struct pollfd)))
    - goto out_fds1;
    + while(pollwalk != NULL) {
    + struct pollfd * fds = (struct pollfd*)(pollwalk+1);
    + int j;
    +
    + for (j=0; j < pollwalk->len; j++, ufds++) {
    + if(__put_user(fds[j].revents, &ufds->revents))
    + goto out_fds;
    + }
    + i -= pollwalk->len;
    + pollwalk = pollwalk->next;
    }
    -
    - fdcount = do_poll(nfds, nchunks, nleft, fds, &table, timeout);
    -
    - /* OK, now copy the revents fields back to user space. */
    - for(i=0; i < nchunks; i++)
    - for (j=0; j < POLLFD_PER_PAGE; j++, ufds++)
    - __put_user((fds[i] + j)->revents, &ufds->revents);
    - if (nleft)
    - for (j=0; j < nleft; j++, ufds++)
    - __put_user((fds[nchunks] + j)->revents, &ufds->revents);
    -
    err = fdcount;
    if (!fdcount && signal_pending(current))
    err = -EINTR;

    -out_fds1:
    - if (nleft)
    - free_page((unsigned long)(fds[nchunks]));
    out_fds:
    - for (i=0; i < nchunks; i++)
    - free_page((unsigned long)(fds[i]));
    - if (nfds != 0)
    - kfree(fds);
    -out:
    + pollwalk = polllist.head.next;
    + while(pollwalk!=NULL) {
    + struct poll_list *pp = pollwalk->next;
    + kfree(pollwalk);
    + pollwalk = pp;
    + }
    poll_freewait(&table);
    return err;
    }
    --- 2.4/include/linux/poll.h Wed Jul 12 20:06:25 2000
    +++ build-2.4/include/linux/poll.h Wed Jul 12 20:16:52 2000
    @@ -23,9 +23,12 @@
    struct poll_table_entry * entry;
    };

    +#define POLL_TABLE_INTERNAL 8
    typedef struct poll_table_struct {
    int error;
    + int nr;
    struct poll_table_page * table;
    + struct poll_table_entry internal[POLL_TABLE_INTERNAL];
    } poll_table;

    #define __MAX_POLL_TABLE_ENTRIES ((PAGE_SIZE - sizeof (struct poll_table_page)) / sizeof (struct poll_table_entry))
    @@ -41,6 +44,7 @@
    static inline void poll_initwait(poll_table* pt)
    {
    pt->error = 0;
    + pt->nr = 0;
    pt->table = NULL;
    }
    extern void poll_freewait(poll_table* pt);





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