On Fri, Feb 16, 2024 at 12:55 AM Chengming Zhou
<[email protected]> wrote:
>
> Dynamic zswap_pool creation may create/reuse to have multiple
> zswap_pools in a list, only the first will be current used.
>
> Each zswap_pool has its own lru and shrinker, which is not
> necessary and has its problem:
>
> 1. When memory has pressure, all shrinker of zswap_pools will
> try to shrink its own lru, there is no order between them.
>
> 2. When zswap limit hit, only the last zswap_pool's shrink_work
> will try to shrink its lru list. The rationale here was to
> try and empty the old pool first so that we can completely
> drop it. However, since we only support exclusive loads now,
> the LRU ordering should be entirely decided by the order of
> stores, so the oldest entries on the LRU will naturally be
> from the oldest pool.
>
> Anyway, having a global lru and shrinker shared by all zswap_pools
> is better and efficient.
>
> Acked-by: Yosry Ahmed <[email protected]>
> Signed-off-by: Chengming Zhou <[email protected]>
> ---
> mm/zswap.c | 171 ++++++++++++++++++++++++-------------------------------------
> 1 file changed, 66 insertions(+), 105 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 62fe307521c9..d275eb523fc4 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -176,14 +176,19 @@ struct zswap_pool {
> struct kref kref;
> struct list_head list;
> struct work_struct release_work;
> - struct work_struct shrink_work;
> struct hlist_node node;
> char tfm_name[CRYPTO_MAX_ALG_NAME];
> +};
> +
> +static struct {
> struct list_lru list_lru;
> - struct mem_cgroup *next_shrink;
> - struct shrinker *shrinker;
> atomic_t nr_stored;
> -};
> + struct shrinker *shrinker;
> + struct work_struct shrink_work;
> + struct mem_cgroup *next_shrink;
> + /* The lock protects next_shrink. */
> + spinlock_t shrink_lock;
> +} zswap;
nit: Is there a reason why we're putting these in a struct instead of
just a bunch of static variables (perhaps prefixed with zswap?)
On 2024/2/20 09:28, Nhat Pham wrote:
> On Fri, Feb 16, 2024 at 12:55 AM Chengming Zhou
> <[email protected]> wrote:
>>
>> Dynamic zswap_pool creation may create/reuse to have multiple
>> zswap_pools in a list, only the first will be current used.
>>
>> Each zswap_pool has its own lru and shrinker, which is not
>> necessary and has its problem:
>>
>> 1. When memory has pressure, all shrinker of zswap_pools will
>> try to shrink its own lru, there is no order between them.
>>
>> 2. When zswap limit hit, only the last zswap_pool's shrink_work
>> will try to shrink its lru list. The rationale here was to
>> try and empty the old pool first so that we can completely
>> drop it. However, since we only support exclusive loads now,
>> the LRU ordering should be entirely decided by the order of
>> stores, so the oldest entries on the LRU will naturally be
>> from the oldest pool.
>>
>> Anyway, having a global lru and shrinker shared by all zswap_pools
>> is better and efficient.
>>
>> Acked-by: Yosry Ahmed <[email protected]>
>> Signed-off-by: Chengming Zhou <[email protected]>
>> ---
>> mm/zswap.c | 171 ++++++++++++++++++++++++-------------------------------------
>> 1 file changed, 66 insertions(+), 105 deletions(-)
>>
>> diff --git a/mm/zswap.c b/mm/zswap.c
>> index 62fe307521c9..d275eb523fc4 100644
>> --- a/mm/zswap.c
>> +++ b/mm/zswap.c
>> @@ -176,14 +176,19 @@ struct zswap_pool {
>> struct kref kref;
>> struct list_head list;
>> struct work_struct release_work;
>> - struct work_struct shrink_work;
>> struct hlist_node node;
>> char tfm_name[CRYPTO_MAX_ALG_NAME];
>> +};
>> +
>> +static struct {
>> struct list_lru list_lru;
>> - struct mem_cgroup *next_shrink;
>> - struct shrinker *shrinker;
>> atomic_t nr_stored;
>> -};
>> + struct shrinker *shrinker;
>> + struct work_struct shrink_work;
>> + struct mem_cgroup *next_shrink;
>> + /* The lock protects next_shrink. */
>> + spinlock_t shrink_lock;
>> +} zswap;
>
> nit: Is there a reason why we're putting these in a struct instead of
> just a bunch of static variables (perhaps prefixed with zswap?)
No reason, both is ok for me. I thought there should be no difference.
But I can change to static variables if it's preferred in kernel. :)