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Wed, 11 Mar 2026 13:20:38 -0700 (PDT) From: Joshua Hahn To: Johannes Weiner Cc: Minchan Kim , Sergey Senozhatsky , Yosry Ahmed , Nhat Pham , Nhat Pham , Chengming Zhou , Andrew Morton , linux-mm@kvack.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 03/11] mm/zsmalloc: Introduce conditional memcg awareness to zs_pool Date: Wed, 11 Mar 2026 13:20:37 -0700 Message-ID: <20260311202037.265101-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 89BF1C0005 X-Rspamd-Server: rspam08 X-Stat-Signature: 7w48kcdnzyinjo3yh4r5r7utybuefkzs X-HE-Tag: 1773260440-711651 X-HE-Meta: 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 wnGDPwyv hwv+9KuUun56qm1dZni0wxz7YCso+d0uKdJui0yVH3R0XdS4HlyjRp60UiwvNA1XafVFZp/NCDKOnQFD3RpYQ95b5aR9JoOTVHIQcNiaryBIKPJB1kaAsB6ExzMIZ2U5P2TIvkkaMqTz/tdh2PdwZQM7F+nHF19KPM57OFIALOy7/weTpaXliqaBndw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 11 Mar 2026 16:16:34 -0400 Johannes Weiner 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 > > Signed-off-by: Joshua Hahn > > --- > > 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