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    Subject[PATCH] mm: swap prefetch more improvements
    Date
    akpm, please queue on top of "mm: swap prefetch improvements"

    ---
    Failed radix_tree_insert wasn't being handled leaving stale kmem.

    The list should be iterated over in the reverse order when prefetching.

    Make the yield within kprefetchd stronger through the use of cond_resched.

    Check that the pos entry hasn't been removed while unlocked.

    Signed-off-by: Con Kolivas <kernel@kolivas.org>

    ---
    mm/swap_prefetch.c | 19 ++++++++++---------
    1 file changed, 10 insertions(+), 9 deletions(-)

    Index: linux-2.6.21-ck1/mm/swap_prefetch.c
    ===================================================================
    --- linux-2.6.21-ck1.orig/mm/swap_prefetch.c 2007-05-14 09:39:37.000000000 +1000
    +++ linux-2.6.21-ck1/mm/swap_prefetch.c 2007-05-14 10:21:47.000000000 +1000
    @@ -117,7 +117,8 @@ void add_to_swapped_list(struct page *pa
    if (likely(!radix_tree_insert(&swapped.swap_tree, index, entry))) {
    list_add(&entry->swapped_list, &swapped.list);
    swapped.count++;
    - }
    + } else
    + kmem_cache_free(swapped.cache, entry);

    out_locked:
    spin_unlock_irqrestore(&swapped.lock, flags);
    @@ -427,7 +428,7 @@ out:
    static enum trickle_return trickle_swap(void)
    {
    enum trickle_return ret = TRICKLE_DELAY;
    - struct list_head *p, *next;
    + struct swapped_entry *pos, *n;
    unsigned long flags;

    if (!prefetch_enabled())
    @@ -440,19 +441,19 @@ static enum trickle_return trickle_swap(
    return TRICKLE_FAILED;

    spin_lock_irqsave(&swapped.lock, flags);
    - list_for_each_safe(p, next, &swapped.list) {
    - struct swapped_entry *entry;
    + list_for_each_entry_safe_reverse(pos, n, &swapped.list, swapped_list) {
    swp_entry_t swp_entry;
    int node;

    spin_unlock_irqrestore(&swapped.lock, flags);
    - might_sleep();
    - if (!prefetch_suitable())
    + /* Yield to anything else running */
    + if (cond_resched() || !prefetch_suitable())
    goto out_unlocked;

    spin_lock_irqsave(&swapped.lock, flags);
    - entry = list_entry(p, struct swapped_entry, swapped_list);
    - node = get_swap_entry_node(entry);
    + if (unlikely(!pos))
    + continue;
    + node = get_swap_entry_node(pos);
    if (!node_isset(node, sp_stat.prefetch_nodes)) {
    /*
    * We found an entry that belongs to a node that is
    @@ -460,7 +461,7 @@ static enum trickle_return trickle_swap(
    */
    continue;
    }
    - swp_entry = entry->swp_entry;
    + swp_entry = pos->swp_entry;
    spin_unlock_irqrestore(&swapped.lock, flags);

    if (trickle_swap_cache_async(swp_entry, node) == TRICKLE_DELAY)
    --
    -ck
    -
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