2021-02-09 18:17:00

by Yang Shi

Subject: [v7 PATCH 10/12] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers

Now nr_deferred is available on per memcg level for memcg aware shrinkers, so don't need
allocate shrinker->nr_deferred for such shrinkers anymore.

The prealloc_memcg_shrinker() would return -ENOSYS if !CONFIG_MEMCG or memcg is disabled
by kernel command line, then shrinker's SHRINKER_MEMCG_AWARE flag would be cleared.
This makes the implementation of this patch simpler.

Acked-by: Vlastimil Babka <[email protected]>
Reviewed-by: Kirill Tkhai <[email protected]>
Signed-off-by: Yang Shi <[email protected]>
---
mm/vmscan.c | 33 ++++++++++++++++++---------------
1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 748aa6e90f83..dfde6e7fd7f5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -338,6 +338,9 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
{
int id, ret = -ENOMEM;

+ if (mem_cgroup_disabled())
+ return -ENOSYS;
+
down_write(&shrinker_rwsem);
/* This may call shrinker, so it must use down_read_trylock() */
id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
@@ -417,7 +420,7 @@ static bool writeback_throttling_sane(struct scan_control *sc)
#else
static int prealloc_memcg_shrinker(struct shrinker *shrinker)
{
- return 0;
+ return -ENOSYS;
}

static void unregister_memcg_shrinker(struct shrinker *shrinker)
@@ -528,8 +531,18 @@ unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
*/
int prealloc_shrinker(struct shrinker *shrinker)
{
- unsigned int size = sizeof(*shrinker->nr_deferred);
+ unsigned int size;
+ int err;

+ if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+ err = prealloc_memcg_shrinker(shrinker);
+ if (err != -ENOSYS)
+ return err;
+
+ shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
+ }
+
+ size = sizeof(*shrinker->nr_deferred);
if (shrinker->flags & SHRINKER_NUMA_AWARE)
size *= nr_node_ids;

@@ -537,26 +550,16 @@ int prealloc_shrinker(struct shrinker *shrinker)
if (!shrinker->nr_deferred)
return -ENOMEM;

- if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
- if (prealloc_memcg_shrinker(shrinker))
- goto free_deferred;
- }

return 0;
-
-free_deferred:
- kfree(shrinker->nr_deferred);
- shrinker->nr_deferred = NULL;
- return -ENOMEM;
}

void free_prealloced_shrinker(struct shrinker *shrinker)
{
- if (!shrinker->nr_deferred)
- return;
-
- if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
unregister_memcg_shrinker(shrinker);
+ return;
+ }

kfree(shrinker->nr_deferred);
shrinker->nr_deferred = NULL;
--
2.26.2

2021-02-10 02:21:10

by Roman Gushchin

Subject: Re: [v7 PATCH 10/12] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers

On Tue, Feb 09, 2021 at 09:46:44AM -0800, Yang Shi wrote:
> Now nr_deferred is available on per memcg level for memcg aware shrinkers, so don't need
> allocate shrinker->nr_deferred for such shrinkers anymore.
>
> The prealloc_memcg_shrinker() would return -ENOSYS if !CONFIG_MEMCG or memcg is disabled
> by kernel command line, then shrinker's SHRINKER_MEMCG_AWARE flag would be cleared.
> This makes the implementation of this patch simpler.
>
> Acked-by: Vlastimil Babka <[email protected]>
> Reviewed-by: Kirill Tkhai <[email protected]>
> Signed-off-by: Yang Shi <[email protected]>

Acked-by: Roman Gushchin <[email protected]>

Thanks!

> ---
> mm/vmscan.c | 33 ++++++++++++++++++---------------
> 1 file changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 748aa6e90f83..dfde6e7fd7f5 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -338,6 +338,9 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> {
> int id, ret = -ENOMEM;
>
> + if (mem_cgroup_disabled())
> + return -ENOSYS;
> +
> down_write(&shrinker_rwsem);
> /* This may call shrinker, so it must use down_read_trylock() */
> id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
> @@ -417,7 +420,7 @@ static bool writeback_throttling_sane(struct scan_control *sc)
> #else
> static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> {
> - return 0;
> + return -ENOSYS;
> }
>
> static void unregister_memcg_shrinker(struct shrinker *shrinker)
> @@ -528,8 +531,18 @@ unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
> */
> int prealloc_shrinker(struct shrinker *shrinker)
> {
> - unsigned int size = sizeof(*shrinker->nr_deferred);
> + unsigned int size;
> + int err;
>
> + if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> + err = prealloc_memcg_shrinker(shrinker);
> + if (err != -ENOSYS)
> + return err;
> +
> + shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
> + }
> +
> + size = sizeof(*shrinker->nr_deferred);
> if (shrinker->flags & SHRINKER_NUMA_AWARE)
> size *= nr_node_ids;
>
> @@ -537,26 +550,16 @@ int prealloc_shrinker(struct shrinker *shrinker)
> if (!shrinker->nr_deferred)
> return -ENOMEM;
>
> - if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> - if (prealloc_memcg_shrinker(shrinker))
> - goto free_deferred;
> - }
>
> return 0;
> -
> -free_deferred:
> - kfree(shrinker->nr_deferred);
> - shrinker->nr_deferred = NULL;
> - return -ENOMEM;
> }
>
> void free_prealloced_shrinker(struct shrinker *shrinker)
> {
> - if (!shrinker->nr_deferred)
> - return;
> -
> - if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> + if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> unregister_memcg_shrinker(shrinker);
> + return;
> + }
>
> kfree(shrinker->nr_deferred);
> shrinker->nr_deferred = NULL;
> --
> 2.26.2
>