mempool_resize and sanity checks

mempool_resize and sanity checks

Post by Balbir Sing » Sun, 17 Mar 2002 09:40:08



In mempool_resize(), I plan to replace the calls
to spin_unlock_irqrestore() -> pool_free -> spin_lock_
irqsave with the new sequence. The newer code
has fewer calls to spin_lock_irqsave and spin_unlock_
restore(). I think the new code should execute faster.

I have tested this code on a UP, if somebody could
test the patch on an SMP box and let me know if it
works, I would be thankful. I also have a sample test
case that uses mempool_resize().

I have also added the BUG_ON sanity checks in
mempool_create().

New Code

if (new_min_nr < pool->min_nr) {
        pool->min_nr = new_min_nr;
        /*      
         * Free possible excess elements.
         */      
        INIT_LIST_HEAD(&tmp_pool_to_free);
        while (pool->curr_nr > pool->min_nr) {
                tmp = pool->elements.next;
                if (tmp == &pool->elements)
                        BUG();  
                list_del(tmp);
                list_add(tmp, &tmp_pool_to_free);
                pool->curr_nr--;
        }      
        spin_unlock_irqrestore(&pool->lock, flags);

        list_for_each(tmp, &tmp_pool_to_free) {
                element = tmp;
                pool->free(element, pool->pool_data);
        }      
        return;

Quote:}      

Original Code

if (new_min_nr < pool->min_nr) {
        pool->min_nr = new_min_nr;
        /*
         * Free possible excess elements.
         */
        while (pool->curr_nr > pool->min_nr) {
                tmp = pool->elements.next;
                if (tmp == &pool->elements)
                        BUG();
                list_del(tmp);
                element = tmp;
                pool->curr_nr--;
                spin_unlock_irqrestore(&pool->lock,
flags);

                pool->free(element, pool->pool_data);

                spin_lock_irqsave(&pool->lock, flags);
        }
        spin_unlock_irqrestore(&pool->lock, flags);
        return;

Quote:}

Diffs are attached.

Balbir

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mempool_resize and sanity checks

Post by Balbir Sing » Sun, 17 Mar 2002 09:50:06


For some reason, it seems that the diffs did not
make it. Resending them

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In mempool_resize(), I plan to replace the calls
to spin_unlock_irqrestore() -> pool_free -> spin_lock_
irqsave with the new sequence. The newer code
has fewer calls to spin_lock_irqsave and spin_unlock_
restore(). I think the new code should execute faster.

I have tested this code on a UP, if somebody could
test the patch on an SMP box and let me know if it
works, I would be thankful. I also have a sample test
case that uses mempool_resize().

I have also added the BUG_ON sanity checks in
mempool_create().

New Code

if (new_min_nr < pool->min_nr) {
        pool->min_nr = new_min_nr;
        /*      
         * Free possible excess elements.
         */      
        INIT_LIST_HEAD(&tmp_pool_to_free);
        while (pool->curr_nr > pool->min_nr) {
                tmp = pool->elements.next;
                if (tmp == &pool->elements)
                        BUG();  
                list_del(tmp);
                list_add(tmp, &tmp_pool_to_free);
                pool->curr_nr--;
        }      
        spin_unlock_irqrestore(&pool->lock, flags);

        list_for_each(tmp, &tmp_pool_to_free) {
                element = tmp;
                pool->free(element, pool->pool_data);
        }      
        return;

Quote:}      

Original Code

if (new_min_nr < pool->min_nr) {
        pool->min_nr = new_min_nr;
        /*
         * Free possible excess elements.
         */
        while (pool->curr_nr > pool->min_nr) {
                tmp = pool->elements.next;
                if (tmp == &pool->elements)
                        BUG();
                list_del(tmp);
                element = tmp;
                pool->curr_nr--;
                spin_unlock_irqrestore(&pool->lock,
flags);

                pool->free(element, pool->pool_data);

                spin_lock_irqsave(&pool->lock, flags);
        }
        spin_unlock_irqrestore(&pool->lock, flags);
        return;

Quote:}

Diffs are attached.

Balbir

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[ mempool.c.diff.txt 1K ]
--- mempool.c   Tue Mar 12 19:21:33 2002

        mempool_t *pool;
        int i;

+       BUG_ON(!alloc_fn);
+       BUG_ON(!free_fn);
+
        pool = kmalloc(sizeof(*pool), GFP_KERNEL);
        if (!pool)

        void *element;
        unsigned long flags;
        struct list_head *tmp;
+       struct list_head tmp_pool_to_free;

        if (new_min_nr <= 0)

                /*
                 * Free possible excess elements.
                 */
+               INIT_LIST_HEAD(&tmp_pool_to_free);
                while (pool->curr_nr > pool->min_nr) {
                        tmp = pool->elements.next;
                        if (tmp == &pool->elements)
                                BUG();
                        list_del(tmp);
-                       element = tmp;
+                       list_add(tmp, &tmp_pool_to_free);
                        pool->curr_nr--;
-                       spin_unlock_irqrestore(&pool->lock, flags);
+               }
+               spin_unlock_irqrestore(&pool->lock, flags);

+               list_for_each(tmp, &tmp_pool_to_free) {
+                       element = tmp;
                        pool->free(element, pool->pool_data);
-
-                       spin_lock_irqsave(&pool->lock, flags);
                }
-               spin_unlock_irqrestore(&pool->lock, flags);
                return;
        }
        delta = new_min_nr - pool->min_nr;