From ea928e9e18da682e9a5bc40aa862bff7ce5ae42e Mon Sep 17 00:00:00 2001 From: Usama Arif Date: Tue, 30 Jun 2026 04:23:33 -0700 Subject: mm/vmpressure: move v1 userspace eventfd code into memcontrol-v1.c MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Clean up mm/vmpressure.c by separating the cgroup v1 userspace eventfd interface from the shared and v2 in-kernel code. Currently, almost half of mm/vmpressure.c exists to serve tree=true: struct vmpressure_event, the events list and its mutex, the work_struct and vmpressure_work_fn that drains tree_scanned/tree_reclaimed, the parent walk, vmpressure_event(), vmpressure_register_event(), vmpressure_unregister_event(), and vmpressure_prio() (which always calls vmpressure() with tree=true). Move it all into mm/memcontrol-v1.c (built only when CONFIG_MEMCG_V1=y) as a single contiguous block, following the per-component layout already used by that file. Keeping the v1 vmpressure code with the rest of the deprecated cgroup v1 memory controller makes the full footprint of the CONFIG_MEMCG_V1 option easy to see in one place, which matters more than component-level file separation for code that has no active development. vmpressure.c keeps the shared bits (constants, vmpressure_calc_level, the runtime hierarchy check, the tree=false body, init/cleanup plumbing) and calls into three small v1 hooks for the tree=true accumulator and the v1 portions of init/cleanup. The hooks have static-inline no-op stubs in include/linux/vmpressure.h for the !MEMCG_V1 case, so callers don't need ifdefs. vmpressure_prio() gets the same treatment, which means vmscan.c's call site disappears at compile time on v2-only kernels. The only #ifdef CONFIG_MEMCG_V1 in source remains around the v1-only fields inside struct vmpressure itself. Memory savings on CONFIG_MEMCG_V1=n (measured with pahole): struct vmpressure : 112B -> 24B struct mem_cgroup : 1664B -> 1536B This split is the first step toward eventually making vmpressure CONFIG_MEMCG_V1 only. The v2 in-kernel socket pressure path (tree=false) cannot be removed today immediately: PSI is not an exact replacement for vmpressure, and switching networking socket-buffer back-off to PSI may regress networking performance or increase memory pressure in workloads that today rely on vmpressure's hysteresis. The medium-term plan is to introduce a PSI-based socket-pressure path, keep vmpressure available for v2 behind a defconfig as an opt-out for several releases, and only then drop the tree=false path entirely, at which point everything that remains of the vmpressure block in mm/memcontrol-v1.c is the whole subsystem. Link: https://lore.kernel.org/20260630112617.1198623-3-usama.arif@linux.dev Signed-off-by: Usama Arif Acked-by: Shakeel Butt Cc: David Hildenbrand Cc: Johannes Weiner Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Michal Koutný Cc: Mike Rapoport Cc: Roman Gushchin Cc: Suren Baghdasaryan Cc: Tejun Heo Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/vmpressure.h | 46 +++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 41 insertions(+), 5 deletions(-) (limited to 'include/linux') diff --git a/include/linux/vmpressure.h b/include/linux/vmpressure.h index faecd5522401..b4d13457bc2a 100644 --- a/include/linux/vmpressure.h +++ b/include/linux/vmpressure.h @@ -13,18 +13,31 @@ struct vmpressure { unsigned long scanned; unsigned long reclaimed; + /* The lock is used to keep the scanned/reclaimed in sync. */ + spinlock_t sr_lock; +#ifdef CONFIG_MEMCG_V1 + /* + * tree=true accumulators feed the v1 userspace eventfd interface + * (memory.pressure_level). Drained by @work. v2 has no equivalent + * interface, so this state is omitted on CONFIG_MEMCG_V1=n builds. + */ unsigned long tree_scanned; unsigned long tree_reclaimed; - /* The lock is used to keep the scanned/reclaimed above in sync. */ - spinlock_t sr_lock; - /* The list of vmpressure_event structs. */ struct list_head events; /* Have to grab the lock on events traversal or modifications. */ struct mutex events_lock; struct work_struct work; +#endif +}; + +enum vmpressure_levels { + VMPRESSURE_LOW = 0, + VMPRESSURE_MEDIUM, + VMPRESSURE_CRITICAL, + VMPRESSURE_NUM_LEVELS, }; struct mem_cgroup; @@ -32,18 +45,41 @@ struct mem_cgroup; #ifdef CONFIG_MEMCG void vmpressure(gfp_t gfp, int order, struct mem_cgroup *memcg, bool tree, unsigned long scanned, unsigned long reclaimed); -extern void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio); - extern void vmpressure_init(struct vmpressure *vmpr); extern void vmpressure_cleanup(struct vmpressure *vmpr); extern struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg); extern struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr); + +/* Shared with the v1 vmpressure block in mm/memcontrol-v1.c. */ +extern const unsigned long vmpressure_win; +extern enum vmpressure_levels vmpressure_calc_level(unsigned long scanned, + unsigned long reclaimed); + +#ifdef CONFIG_MEMCG_V1 +extern void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio); extern int vmpressure_register_event(struct mem_cgroup *memcg, struct eventfd_ctx *eventfd, const char *args); extern void vmpressure_unregister_event(struct mem_cgroup *memcg, struct eventfd_ctx *eventfd); + +/* v1 hooks called from mm/vmpressure.c; no-ops below when !MEMCG_V1. */ +extern void vmpressure_v1_init(struct vmpressure *vmpr); +extern void vmpressure_v1_cleanup(struct vmpressure *vmpr); +extern void vmpressure_v1_account_tree(struct vmpressure *vmpr, + unsigned long scanned, + unsigned long reclaimed); #else +static inline void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, + int prio) {} +static inline void vmpressure_v1_init(struct vmpressure *vmpr) {} +static inline void vmpressure_v1_cleanup(struct vmpressure *vmpr) {} +static inline void vmpressure_v1_account_tree(struct vmpressure *vmpr, + unsigned long scanned, + unsigned long reclaimed) {} +#endif /* CONFIG_MEMCG_V1 */ + +#else /* !CONFIG_MEMCG */ static inline void vmpressure(gfp_t gfp, int order, struct mem_cgroup *memcg, bool tree, unsigned long scanned, unsigned long reclaimed) {} -- cgit v1.2.3