Hello,
On 10/16/2014 05:17 AM, Andrew Morton wrote:
On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin <heesub.shin@xxxxxxxxxxx> wrote:
When zbud is initialized through the zpool wrapper, pool->ops which
points to user-defined operations is always set regardless of whether it
is specified from the upper layer. This causes zbud_reclaim_page() to
iterate its loop for evicting pool pages out without any gain.
This patch sets the user-defined ops only when it is needed, so that
zbud_reclaim_page() can bail out the reclamation loop earlier if there
is no user-defined operations specified.
Which callsite is calling zbud_zpool_create(..., NULL)?
Currently nowhere. zswap is the only user of zbud and always passes a
pointer to user-defined operation on pool creation. In addition, there
may be less possibility that pool shrinking is requested by users who
did not provide the user-defined ops. So, we may not need to worry much
about what I wrote in the changelog. However, it is definitely weird to
pass an argument, zpool_ops, which even will not be referenced by
zbud_zpool_create(). Above all, it would be more useful to avoid the
possibility in the future rather than just ignoring it.
regards,
heesub
...
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {
static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
{
- return zbud_create_pool(gfp, &zbud_zpool_ops);
+ return zbud_create_pool(gfp, zpool_ops ? &zbud_zpool_ops : NULL);
}
static void zbud_zpool_destroy(void *pool)
--
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