On 13.12.2016 15:39, Andrey Ryabinin wrote:
> If tcache is empty we can bail out immediately from
> tcache_cleancache_[get_page, invalidate_page,invalidate_inode]().
> As a fast way of identifying empty tcache this patch adds global atomic
> counter of tcache nodes.
>
> https://jira.sw.ru/browse/PSBM-56475
>
> Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
Reviewed-by: Kirill Tkhai <ktk...@virtuozzo.com>
> ---
>
> Changes since v1:
> - switch to long counter to prevent possible overflows
> Changes since v2:
> - use *_dec() insrtead of bogus _inc() in tcache_node_release_fn()
> in v2 version
>
> mm/tcache.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/mm/tcache.c b/mm/tcache.c
> index cec5a4e..c7613b2 100644
> --- a/mm/tcache.c
> +++ b/mm/tcache.c
> @@ -98,6 +98,8 @@ struct tcache_pool {
> struct tcache_pool_nodeinfo nodeinfo[0];
> };
>
> +static atomic_long_t nr_tcache_nodes;
> +
> /*
> * Tcache nodes correspond to inodes. A node is created automatically when a
> * new page is added to the cache (cleancache_put_page) and destroyed either
> @@ -561,6 +563,7 @@ retry:
> node->pool = pool;
> node->key = *key;
> atomic_long_inc(&pool->nr_nodes);
> + atomic_long_inc(&nr_tcache_nodes);
> __tcache_insert_node(&tree->root, node, rb_link, rb_parent);
> }
> spin_unlock_irqrestore(&tree->lock, flags);
> @@ -590,6 +593,7 @@ static void tcache_node_release_fn(struct kref *kref)
> __tcache_delete_node(&tree->root, node);
> spin_unlock(&tree->lock);
>
> + atomic_long_dec(&nr_tcache_nodes);
> atomic_long_dec(&node->pool->nr_nodes);
> kfree(node);
> }
> @@ -1168,6 +1172,9 @@ static int tcache_cleancache_get_page(int pool_id,
> struct tcache_node *node;
> struct page *cache_page = NULL;
>
> + if (!atomic_long_read(&nr_tcache_nodes))
> + return -1;
> +
> node = tcache_get_node_and_pool(pool_id, &key, false);
> if (node) {
> cache_page = tcache_detach_page(node, index, true);
> @@ -1192,6 +1199,9 @@ static void tcache_cleancache_invalidate_page(int
> pool_id,
> struct tcache_node *node;
> struct page *page;
>
> + if (!atomic_long_read(&nr_tcache_nodes))
> + return;
> +
> node = tcache_get_node_and_pool(pool_id, &key, false);
> if (node) {
> page = tcache_detach_page(node, index, false);
> @@ -1206,6 +1216,9 @@ static void tcache_cleancache_invalidate_inode(int
> pool_id,
> {
> struct tcache_pool *pool;
>
> + if (!atomic_long_read(&nr_tcache_nodes))
> + return;
> +
> pool = tcache_get_pool(pool_id);
> if (pool) {
> tcache_invalidate_node(pool, &key);
>
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