On Mon, Nov 6, 2023 at 12:26 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > > On Mon, Nov 6, 2023 at 10:32 AM Nhat Pham <nphamcs@xxxxxxxxx> wrote: > > > > From: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx> > > > > Currently, we only have a single global LRU for zswap. This makes it > > impossible to perform worload-specific shrinking - an memcg cannot > > determine which pages in the pool it owns, and often ends up writing > > pages from other memcgs. This issue has been previously observed in > > practice and mitigated by simply disabling memcg-initiated shrinking: > > > > https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@xxxxxxxxx/T/#u > > > > This patch fully resolves the issue by replacing the global zswap LRU > > with memcg- and NUMA-specific LRUs, and modify the reclaim logic: > > > > a) When a store attempt hits an memcg limit, it now triggers a > > synchronous reclaim attempt that, if successful, allows the new > > hotter page to be accepted by zswap. > > b) If the store attempt instead hits the global zswap limit, it will > > trigger an asynchronous reclaim attempt, in which an memcg is > > selected for reclaim in a round-robin-like fashion. > > > > Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx> > > Co-developed-by: Nhat Pham <nphamcs@xxxxxxxxx> > > Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx> > > --- > > include/linux/memcontrol.h | 5 + > > include/linux/zswap.h | 2 + > > mm/memcontrol.c | 2 + > > mm/swap.h | 3 +- > > mm/swap_state.c | 24 +++- > > mm/zswap.c | 252 +++++++++++++++++++++++++++++-------- > > 6 files changed, 227 insertions(+), 61 deletions(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index 55c85f952afd..95f6c9e60ed1 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -1187,6 +1187,11 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page) > > return NULL; > > } > > > > +static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg) > > +{ > > + return NULL; > > +} > > + > > static inline bool folio_memcg_kmem(struct folio *folio) > > { > > return false; > > diff --git a/include/linux/zswap.h b/include/linux/zswap.h > > index 2a60ce39cfde..e571e393669b 100644 > > --- a/include/linux/zswap.h > > +++ b/include/linux/zswap.h > > @@ -15,6 +15,7 @@ bool zswap_load(struct folio *folio); > > void zswap_invalidate(int type, pgoff_t offset); > > void zswap_swapon(int type); > > void zswap_swapoff(int type); > > +void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg); > > > > #else > > > > @@ -31,6 +32,7 @@ static inline bool zswap_load(struct folio *folio) > > static inline void zswap_invalidate(int type, pgoff_t offset) {} > > static inline void zswap_swapon(int type) {} > > static inline void zswap_swapoff(int type) {} > > +static inline void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg) {} > > > > #endif > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 6f7fc0101252..2ef49b471a16 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -5640,6 +5640,8 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) > > page_counter_set_min(&memcg->memory, 0); > > page_counter_set_low(&memcg->memory, 0); > > > > + zswap_memcg_offline_cleanup(memcg); > > I think the "_cleanup" suffix is unnecessary. I guess most calls made > here are cleanup calls anyway. I don't have any strong preference here. > > > + > > memcg_offline_kmem(memcg); > > reparent_shrinker_deferred(memcg); > > wb_memcg_offline(memcg); > > diff --git a/mm/swap.h b/mm/swap.h > > index 73c332ee4d91..c0dc73e10e91 100644 > > --- a/mm/swap.h > > +++ b/mm/swap.h > > > @@ -289,15 +291,42 @@ static void zswap_update_total_size(void) > > zswap_pool_total_size = total; > > } > > > > +/* should be called under RCU */ > > +static inline struct mem_cgroup *get_mem_cgroup_from_entry(struct zswap_entry *entry) > > Do not use "get" in the name if we are not actually taking a ref here. > mem_cgroup_from_entry()? That works for me. > > > +{ > > + return entry->objcg ? obj_cgroup_memcg(entry->objcg) : NULL; > > +} > > + > > +static inline int entry_to_nid(struct zswap_entry *entry) > > +{ > > + return page_to_nid(virt_to_page(entry)); > > +} > > + > > +void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg) > > +{ > > + struct zswap_pool *pool; > > + > > + /* lock out zswap pools list modification */ > > + spin_lock(&zswap_pools_lock); > > + list_for_each_entry(pool, &zswap_pools, list) { > > + spin_lock(&pool->next_shrink_lock); > > This lock is only needed to synchronize updating pool->next_shrink, > right? Can we just use atomic operations instead? (e.g. cmpxchg()). I'm not entirely sure. I think in the pool destroy path, we have to also put the next_shrink memcg, so there's that. > > > + if (pool->next_shrink == memcg) > > + pool->next_shrink = > > + mem_cgroup_iter(NULL, pool->next_shrink, NULL, true); > > + spin_unlock(&pool->next_shrink_lock); > > + } > > + spin_unlock(&zswap_pools_lock); > > +} > > + > > /********************************* > > * zswap entry functions > > **********************************/ > > static struct kmem_cache *zswap_entry_cache; > > > > -static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp) > > +static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp, int nid) > > { > > struct zswap_entry *entry; > > - entry = kmem_cache_alloc(zswap_entry_cache, gfp); > > + entry = kmem_cache_alloc_node(zswap_entry_cache, gfp, nid); > > if (!entry) > > return NULL; > > entry->refcount = 1; > [..] > > @@ -1233,15 +1369,15 @@ bool zswap_store(struct folio *folio) > > zswap_invalidate_entry(tree, dupentry); > > } > > spin_unlock(&tree->lock); > > - > > - /* > > - * XXX: zswap reclaim does not work with cgroups yet. Without a > > - * cgroup-aware entry LRU, we will push out entries system-wide based on > > - * local cgroup limits. > > - */ > > objcg = get_obj_cgroup_from_folio(folio); > > - if (objcg && !obj_cgroup_may_zswap(objcg)) > > - goto reject; > > + if (objcg && !obj_cgroup_may_zswap(objcg)) { > > + memcg = get_mem_cgroup_from_objcg(objcg); > > + if (shrink_memcg(memcg)) { > > + mem_cgroup_put(memcg); > > + goto reject; > > + } > > + mem_cgroup_put(memcg); > > Can we just use RCU here as well? (same around memcg_list_lru_alloc() > call below). For memcg_list_lru_alloc(): there's potentially sleeping in that piece of code I believe? I believe at the very least we'll have to use this gfp_t flag for it to be rcu-safe: GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN not sure the Same go for this particular place IIRC - there's some sleeping done in zswap_writeback_entry(), correct? > > > + } > > > > /* reclaim space if needed */ > > if (zswap_is_full()) { > > @@ -1258,7 +1394,7 @@ bool zswap_store(struct folio *folio) > > } > > > > /* allocate entry */ > > - entry = zswap_entry_cache_alloc(GFP_KERNEL); > > + entry = zswap_entry_cache_alloc(GFP_KERNEL, page_to_nid(page)); > > if (!entry) { > > zswap_reject_kmemcache_fail++; > > goto reject; > > @@ -1285,6 +1421,15 @@ bool zswap_store(struct folio *folio) > > if (!entry->pool) > > goto freepage; > > > > + if (objcg) { > > + memcg = get_mem_cgroup_from_objcg(objcg); > > + if (memcg_list_lru_alloc(memcg, &entry->pool->list_lru, GFP_KERNEL)) { > > + mem_cgroup_put(memcg); > > + goto put_pool; > > + } > > + mem_cgroup_put(memcg); > > + } > > + > > /* compress */ > > acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); > >
