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From: Ridong Chen In-Reply-To: <20260710111224.2355668-1-ridong.chen@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: g99ksr8cgpmu1pdy434bbb6zu5ppu45q X-Rspamd-Queue-Id: 40C48120005 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783761480-884427 X-HE-Meta: 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 14rJg1b6 86RCjcTlKU/kOx14L0/xJ6ugrjDBueigGfEO53m5jfDcXTuJpCbpIkm6V9PGnMVTWQhRgKNakqrN97HnBmX0PIDj76wvPQL3/OufY7YeEvzIQohY6HxchCHDRWXir/fgM2w1JQLGpR8A20UPuV+48dnzNjq2K35Tbw4t8vtTh4vH2a/eTpyrvHAYK4zGI66uP5pnucVxqYNdDFYRW+O0dZkTFzel3sA2Q7mlJhQhaoHoSpesJSChADTD+ATtqWwqB1aEZSYzoApT+/6kQsTPgwghZx4IgsX2NWhtB7Qx0gO7Ay8U= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/10/2026 7:12 PM, Ridong wrote: > From: Ridong Chen > > The per-memcg swappiness knob is v1-only; v2 always uses global > vm_swappiness and ignores the per-cgroup field. > > Guard memcg->swappiness with CONFIG_MEMCG_V1, and move the helper > to memcontrol.h where it belongs. > > No functional change for v1; v2-only kernels drop the unused field. > > Signed-off-by: Ridong Chen > --- > include/linux/memcontrol.h | 25 +++++++++++++++++++++++-- > include/linux/swap.h | 19 ------------------- > mm/memcontrol.c | 3 +-- > 3 files changed, 24 insertions(+), 23 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index e1f46a0016fc..f59614956f96 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -239,8 +239,6 @@ struct mem_cgroup { > */ > bool oom_group; > > - int swappiness; > - > /* memory.events and memory.events.local */ > struct cgroup_file events_file; > struct cgroup_file events_local_file; > @@ -318,6 +316,9 @@ struct mem_cgroup { > /* List of events which userspace want to receive */ > struct list_head event_list; > spinlock_t event_list_lock; > + > + int swappiness; > + > #endif /* CONFIG_MEMCG_V1 */ > > struct mem_cgroup_per_node *nodeinfo[]; > @@ -365,6 +366,9 @@ enum objext_flags { > > #define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1) > > +/* Defined in mm/vmscan.c; used by mem_cgroup_swappiness(). */ > +extern int vm_swappiness; > + > #ifdef CONFIG_MEMCG > /* > * After the initialization objcg->memcg is always pointing at > @@ -1440,6 +1444,23 @@ static inline void mem_cgroup_flush_workqueue(void) { } > static inline int mem_cgroup_init(void) { return 0; } > #endif /* CONFIG_MEMCG */ > > +static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) > +{ > +#ifdef CONFIG_MEMCG_V1 > + /* Cgroup2 doesn't have per-cgroup swappiness */ > + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + return READ_ONCE(vm_swappiness); > + > + /* root ? */ > + if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) > + return READ_ONCE(vm_swappiness); > + > + return READ_ONCE(memcg->swappiness); > +#else > + return READ_ONCE(vm_swappiness); > +#endif > +} > + > /* > * Extended information for slab objects stored as an array in page->memcg_data > * if MEMCG_DATA_OBJEXTS is set. > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 3f31b6a56788..f27e73f29195 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -366,7 +366,6 @@ extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem, > pg_data_t *pgdat, > unsigned long *nr_scanned); > extern unsigned long shrink_all_memory(unsigned long nr_pages); > -extern int vm_swappiness; > long remove_mapping(struct address_space *mapping, struct folio *folio); > > #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) > @@ -530,25 +529,7 @@ static inline int add_swap_extent(struct swap_info_struct *sis, > } > #endif /* CONFIG_SWAP */ > #ifdef CONFIG_MEMCG > -static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) > -{ > - /* Cgroup2 doesn't have per-cgroup swappiness */ > - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > - return READ_ONCE(vm_swappiness); > - > - /* root ? */ > - if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) > - return READ_ONCE(vm_swappiness); > - > - return READ_ONCE(memcg->swappiness); > -} > - > void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid); > -#else > -static inline int mem_cgroup_swappiness(struct mem_cgroup *mem) > -{ > - return READ_ONCE(vm_swappiness); > -} > #endif > > #if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 938f190a98fe..2d659b76cd77 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4174,11 +4174,10 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) > #endif > page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX); > if (parent) { > - WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); > - > page_counter_init(&memcg->memory, &parent->memory, memcg_on_dfl); > page_counter_init(&memcg->swap, &parent->swap, false); > #ifdef CONFIG_MEMCG_V1 > + WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); > memcg->memory.track_failcnt = !memcg_on_dfl; > WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable)); > page_counter_init(&memcg->kmem, &parent->kmem, false); I have resent this patch [1], as I found another issue related to it. [1] https://lore.kernel.org/linux-mm/20260711091157.306070-1-ridong.chen@linux.dev/ -- Best regards, Ridong