Introduce 3 new fields to struct zs_pool to allow individual zpools to
be "memcg-aware": memcg_aware, compressed_stat, and uncompressed_stat.
memcg_aware is used in later patches to determine whether memory
should be allocated to keep track of per-compresed object objgs.
compressed_stat and uncompressed_stat are enum indices that point into
memcg (node) stats that zsmalloc will account towards.
In reality, these fields help distinguish between the two users of
zsmalloc, zswap and zram. The enum indices compressed_stat and
uncompressed_stat are parametrized to minimize zswap-specific hardcoding
in zsmalloc.
Suggested-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
---
drivers/block/zram/zram_drv.c | 3 ++-
include/linux/zsmalloc.h | 5 ++++-
mm/zsmalloc.c | 13 ++++++++++++-
mm/zswap.c | 3 ++-
4 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index bca33403fc8b..d1eae5c20df7 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1980,7 +1980,8 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
if (!zram->table)
return false;
- zram->mem_pool = zs_create_pool(zram->disk->disk_name);
+ /* zram does not support memcg accounting */
+ zram->mem_pool = zs_create_pool(zram->disk->disk_name, false, 0, 0);
if (!zram->mem_pool) {
vfree(zram->table);
zram->table = NULL;
diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
index 478410c880b1..24fb2e0fdf67 100644
--- a/include/linux/zsmalloc.h
+++ b/include/linux/zsmalloc.h
@@ -23,8 +23,11 @@ struct zs_pool_stats {
struct zs_pool;
struct scatterlist;
+enum memcg_stat_item;
-struct zs_pool *zs_create_pool(const char *name);
+struct zs_pool *zs_create_pool(const char *name, bool memcg_aware,
+ enum memcg_stat_item compressed_stat,
+ enum memcg_stat_item uncompressed_stat);
void zs_destroy_pool(struct zs_pool *pool);
unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags,
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 7758486e1d06..3f0f42b78314 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -214,6 +214,9 @@ struct zs_pool {
#ifdef CONFIG_COMPACTION
struct work_struct free_work;
#endif
+ bool memcg_aware;
+ enum memcg_stat_item compressed_stat;
+ enum memcg_stat_item uncompressed_stat;
/* protect zspage migration/compaction */
rwlock_t lock;
atomic_t compaction_in_progress;
@@ -2050,6 +2053,9 @@ static int calculate_zspage_chain_size(int class_size)
/**
* zs_create_pool - Creates an allocation pool to work from.
* @name: pool name to be created
+ * @memcg_aware: whether the consumer of this pool will account memcg stats
+ * @compressed_stat: compressed memcontrol stat item to account
+ * @uncompressed_stat: uncompressed memcontrol stat item to account
*
* This function must be called before anything when using
* the zsmalloc allocator.
@@ -2057,7 +2063,9 @@ static int calculate_zspage_chain_size(int class_size)
* On success, a pointer to the newly created pool is returned,
* otherwise NULL.
*/
-struct zs_pool *zs_create_pool(const char *name)
+struct zs_pool *zs_create_pool(const char *name, bool memcg_aware,
+ enum memcg_stat_item compressed_stat,
+ enum memcg_stat_item uncompressed_stat)
{
int i;
struct zs_pool *pool;
@@ -2071,6 +2079,9 @@ struct zs_pool *zs_create_pool(const char *name)
rwlock_init(&pool->lock);
atomic_set(&pool->compaction_in_progress, 0);
+ pool->memcg_aware = memcg_aware;
+ pool->compressed_stat = compressed_stat;
+ pool->uncompressed_stat = uncompressed_stat;
pool->name = kstrdup(name, GFP_KERNEL);
if (!pool->name)
goto err;
diff --git a/mm/zswap.c b/mm/zswap.c
index e6ec3295bdb0..ff9abaa8aa38 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -257,7 +257,8 @@ static struct zswap_pool *zswap_pool_create(char *compressor)
/* unique name for each pool specifically required by zsmalloc */
snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
- pool->zs_pool = zs_create_pool(name);
+ pool->zs_pool = zs_create_pool(name, true, MEMCG_ZSWAP_B,
+ MEMCG_ZSWAPPED);
if (!pool->zs_pool)
goto error;
--
2.52.0On Wed, Mar 11, 2026 at 12:51:40PM -0700, Joshua Hahn wrote:
> Introduce 3 new fields to struct zs_pool to allow individual zpools to
> be "memcg-aware": memcg_aware, compressed_stat, and uncompressed_stat.
>
> memcg_aware is used in later patches to determine whether memory
> should be allocated to keep track of per-compresed object objgs.
> compressed_stat and uncompressed_stat are enum indices that point into
> memcg (node) stats that zsmalloc will account towards.
>
> In reality, these fields help distinguish between the two users of
> zsmalloc, zswap and zram. The enum indices compressed_stat and
> uncompressed_stat are parametrized to minimize zswap-specific hardcoding
> in zsmalloc.
>
> Suggested-by: Yosry Ahmed <yosry@kernel.org>
> Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> ---
> drivers/block/zram/zram_drv.c | 3 ++-
> include/linux/zsmalloc.h | 5 ++++-
> mm/zsmalloc.c | 13 ++++++++++++-
> mm/zswap.c | 3 ++-
> 4 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index bca33403fc8b..d1eae5c20df7 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1980,7 +1980,8 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
> if (!zram->table)
> return false;
>
> - zram->mem_pool = zs_create_pool(zram->disk->disk_name);
> + /* zram does not support memcg accounting */
> + zram->mem_pool = zs_create_pool(zram->disk->disk_name, false, 0, 0);
It's a bit awkward that 0 is valid (MEMCG_SWAP). Plus you store these
values in every pool, even though they're always the same for all
zswap pools.
How about:
/* zsmalloc.h */
struct zs_memcg_params {
enum memcg_stat_item compressed;
enum memcg_stat_item uncompressed;
};
struct zs_pool *zs_create_pool(const char *name, struct zs_memcg_params *memcg_params);
/* zswap.c */
static struct zs_memcg_params zswap_memcg_params = {
.compressed = MEMCG_ZSWAP_B,
.uncompressed = MEMCG_ZSWAPPED,
};
then pass &zswap_memcg_params from zswap and NULL from zram.
> @@ -2071,6 +2079,9 @@ struct zs_pool *zs_create_pool(const char *name)
> rwlock_init(&pool->lock);
> atomic_set(&pool->compaction_in_progress, 0);
>
> + pool->memcg_aware = memcg_aware;
> + pool->compressed_stat = compressed_stat;
> + pool->uncompressed_stat = uncompressed_stat;
pool->memcg_params = memcg_params;
And then use if (pool->memcg_params) to gate in zsmalloc.c.
> It's a bit awkward that 0 is valid (MEMCG_SWAP). Plus you store these
> values in every pool, even though they're always the same for all
> zswap pools.
>
> How about:
>
> /* zsmalloc.h */
> struct zs_memcg_params {
> enum memcg_stat_item compressed;
> enum memcg_stat_item uncompressed;
> };
> struct zs_pool *zs_create_pool(const char *name, struct zs_memcg_params *memcg_params);
>
> /* zswap.c */
> static struct zs_memcg_params zswap_memcg_params = {
> .compressed = MEMCG_ZSWAP_B,
> .uncompressed = MEMCG_ZSWAPPED,
> };
>
> then pass &zswap_memcg_params from zswap and NULL from zram.
>
> > @@ -2071,6 +2079,9 @@ struct zs_pool *zs_create_pool(const char *name)
> > rwlock_init(&pool->lock);
> > atomic_set(&pool->compaction_in_progress, 0);
> >
> > + pool->memcg_aware = memcg_aware;
> > + pool->compressed_stat = compressed_stat;
> > + pool->uncompressed_stat = uncompressed_stat;
>
> pool->memcg_params = memcg_params;
>
> And then use if (pool->memcg_params) to gate in zsmalloc.c.
I like this.
I also didn't like the suggested prototype for zs_create_pool(), and
didn't like that compressed_stat and uncompressed_stat did not have
memcg anywhere in the name. Was going to suggest adding a warning if
memcg_aware=false but the stat indices are non-zero, but your
suggestion is so much cleaner.
On Wed, 11 Mar 2026 16:16:34 -0400 Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Wed, Mar 11, 2026 at 12:51:40PM -0700, Joshua Hahn wrote:
> > Introduce 3 new fields to struct zs_pool to allow individual zpools to
> > be "memcg-aware": memcg_aware, compressed_stat, and uncompressed_stat.
> >
> > memcg_aware is used in later patches to determine whether memory
> > should be allocated to keep track of per-compresed object objgs.
> > compressed_stat and uncompressed_stat are enum indices that point into
> > memcg (node) stats that zsmalloc will account towards.
> >
> > In reality, these fields help distinguish between the two users of
> > zsmalloc, zswap and zram. The enum indices compressed_stat and
> > uncompressed_stat are parametrized to minimize zswap-specific hardcoding
> > in zsmalloc.
> >
> > Suggested-by: Yosry Ahmed <yosry@kernel.org>
> > Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> > ---
> > drivers/block/zram/zram_drv.c | 3 ++-
> > include/linux/zsmalloc.h | 5 ++++-
> > mm/zsmalloc.c | 13 ++++++++++++-
> > mm/zswap.c | 3 ++-
> > 4 files changed, 20 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index bca33403fc8b..d1eae5c20df7 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -1980,7 +1980,8 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
> > if (!zram->table)
> > return false;
> >
> > - zram->mem_pool = zs_create_pool(zram->disk->disk_name);
> > + /* zram does not support memcg accounting */
> > + zram->mem_pool = zs_create_pool(zram->disk->disk_name, false, 0, 0);
Hello Johannes,
Thank you for your review! I hope you are doing well : -)
> It's a bit awkward that 0 is valid (MEMCG_SWAP). Plus you store these
> values in every pool, even though they're always the same for all
> zswap pools.
Agreed. Originally I thought of removing memcg_aware and doing a bitwise
OR check of the two stats, but thought this was also a bit strange
(also because 0 is not a valid enum state for memcg_stat_item anyways)
> How about:
>
> /* zsmalloc.h */
> struct zs_memcg_params {
> enum memcg_stat_item compressed;
> enum memcg_stat_item uncompressed;
> };
> struct zs_pool *zs_create_pool(const char *name, struct zs_memcg_params *memcg_params);
>
> /* zswap.c */
> static struct zs_memcg_params zswap_memcg_params = {
> .compressed = MEMCG_ZSWAP_B,
> .uncompressed = MEMCG_ZSWAPPED,
> };
>
> then pass &zswap_memcg_params from zswap and NULL from zram.
>
> > @@ -2071,6 +2079,9 @@ struct zs_pool *zs_create_pool(const char *name)
> > rwlock_init(&pool->lock);
> > atomic_set(&pool->compaction_in_progress, 0);
> >
> > + pool->memcg_aware = memcg_aware;
> > + pool->compressed_stat = compressed_stat;
> > + pool->uncompressed_stat = uncompressed_stat;
>
> pool->memcg_params = memcg_params;
>
> And then use if (pool->memcg_params) to gate in zsmalloc.c.
These definitely look a lot cleaner. Will make these changes in v3!
Thanks again. I hope you have a great day!
Joshua
On Wed, Mar 11, 2026 at 12:51 PM Joshua Hahn <joshua.hahnjy@gmail.com> wrote: > > Introduce 3 new fields to struct zs_pool to allow individual zpools to > be "memcg-aware": memcg_aware, compressed_stat, and uncompressed_stat. > > memcg_aware is used in later patches to determine whether memory > should be allocated to keep track of per-compresed object objgs. > compressed_stat and uncompressed_stat are enum indices that point into > memcg (node) stats that zsmalloc will account towards. > > In reality, these fields help distinguish between the two users of > zsmalloc, zswap and zram. The enum indices compressed_stat and > uncompressed_stat are parametrized to minimize zswap-specific hardcoding > in zsmalloc. > > Suggested-by: Yosry Ahmed <yosry@kernel.org> > Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com> Zswap side LGTM :) And for that: Acked-by: Nhat Pham <nphamcs@gmail.com>
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