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.
Signed-off-by: Heesub Shin <[email protected]>
---
mm/zbud.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/zbud.c b/mm/zbud.c
index ecf1dbe..db8de74 100644
--- 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)
--
1.9.1
On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin <[email protected]> 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)?
> ...
> --- 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)
Hello,
On 10/16/2014 05:17 AM, Andrew Morton wrote:
> On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin <[email protected]> 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)
>
>
On Wed, Oct 15, 2014 at 6:00 AM, Heesub Shin <[email protected]> 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.
Though the only current user (zswap) always passes an ops param, other
future users may not and this is the right way to handle it. thanks!
>
> Signed-off-by: Heesub Shin <[email protected]>
Acked-by: Dan Streetman <[email protected]>
> ---
> mm/zbud.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/zbud.c b/mm/zbud.c
> index ecf1dbe..db8de74 100644
> --- 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)
> --
> 1.9.1
>