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Wed, 05 Apr 2023 11:54:33 -0700 (PDT) Date: Wed, 5 Apr 2023 18:54:27 +0000 In-Reply-To: <20230405185427.1246289-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230405185427.1246289-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230405185427.1246289-3-yosryahmed@google.com> Subject: [PATCH v5 2/2] mm: vmscan: refactor reclaim_state helpers From: Yosry Ahmed To: Andrew Morton , Alexander Viro , "Darrick J. Wong" , Christoph Lameter , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Matthew Wilcox (Oracle)" , Miaohe Lin , David Hildenbrand , Johannes Weiner , Peter Xu , NeilBrown , Shakeel Butt , Michal Hocko , Yu Zhao , Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Yosry Ahmed X-Rspamd-Queue-Id: 42482100011 X-Stat-Signature: tdn5erwuowehfwmc3aduxme7u5bqb9ab X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1680720874-820682 X-HE-Meta: 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 rELNAt2G 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: During reclaim, we keep track of pages reclaimed from other means than LRU-based reclaim through scan_control->reclaim_state->reclaimed_slab, which we stash a pointer to in current task_struct. However, we keep track of more than just reclaimed slab pages through this. We also use it for clean file pages dropped through pruned inodes, and xfs buffer pages freed. Rename reclaimed_slab to reclaimed, and add a helper function that wraps updating it through current, so that future changes to this logic are contained within mm/vmscan.c. Additionally, add a flush_reclaim_state() helper to wrap using reclaim_state->reclaimed to updated sc->nr_reclaimed, and use that helper to add an elaborate comment about why we only do the update for global reclaim. Finally, move set_task_reclaim_state() next to flush_reclaim_state() so that all reclaim_state helpers are in close proximity for easier readability. Signed-off-by: Yosry Ahmed --- fs/inode.c | 3 +- fs/xfs/xfs_buf.c | 3 +- include/linux/swap.h | 17 +++++++++- mm/slab.c | 3 +- mm/slob.c | 6 ++-- mm/slub.c | 5 ++- mm/vmscan.c | 75 ++++++++++++++++++++++++++++++++------------ 7 files changed, 78 insertions(+), 34 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index 4558dc2f13557..e60fcc41faf17 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -864,8 +864,7 @@ static enum lru_status inode_lru_isolate(struct list_head *item, __count_vm_events(KSWAPD_INODESTEAL, reap); else __count_vm_events(PGINODESTEAL, reap); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += reap; + mm_account_reclaimed_pages(reap); } iput(inode); spin_lock(lru_lock); diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 54c774af6e1c6..15d1e5a7c2d34 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -286,8 +286,7 @@ xfs_buf_free_pages( if (bp->b_pages[i]) __free_page(bp->b_pages[i]); } - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += bp->b_page_count; + mm_account_reclaimed_pages(bp->b_page_count); if (bp->b_pages != bp->b_page_array) kmem_free(bp->b_pages); diff --git a/include/linux/swap.h b/include/linux/swap.h index 209a425739a9f..e131ac155fb95 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -153,13 +153,28 @@ union swap_header { * memory reclaim */ struct reclaim_state { - unsigned long reclaimed_slab; + /* pages reclaimed outside of LRU-based reclaim */ + unsigned long reclaimed; #ifdef CONFIG_LRU_GEN /* per-thread mm walk data */ struct lru_gen_mm_walk *mm_walk; #endif }; +/* + * mm_account_reclaimed_pages(): account reclaimed pages outside of LRU-based + * reclaim + * @pages: number of pages reclaimed + * + * If the current process is undergoing a reclaim operation, increment the + * number of reclaimed pages by @pages. + */ +static inline void mm_account_reclaimed_pages(unsigned long pages) +{ + if (current->reclaim_state) + current->reclaim_state->reclaimed += pages; +} + #ifdef __KERNEL__ struct address_space; diff --git a/mm/slab.c b/mm/slab.c index dabc2a671fc6f..64bf1de817b24 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1392,8 +1392,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab) smp_wmb(); __folio_clear_slab(folio); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += 1 << order; + mm_account_reclaimed_pages(1 << order); unaccount_slab(slab, order, cachep); __free_pages(&folio->page, order); } diff --git a/mm/slob.c b/mm/slob.c index fe567fcfa3a39..79cc8680c973c 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -61,7 +61,7 @@ #include #include -#include /* struct reclaim_state */ +#include /* mm_account_reclaimed_pages() */ #include #include #include @@ -211,9 +211,7 @@ static void slob_free_pages(void *b, int order) { struct page *sp = virt_to_page(b); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += 1 << order; - + mm_account_reclaimed_pages(1 << order); mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B, -(PAGE_SIZE << order)); __free_pages(sp, order); diff --git a/mm/slub.c b/mm/slub.c index 39327e98fce34..7aa30eef82350 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -11,7 +11,7 @@ */ #include -#include /* struct reclaim_state */ +#include /* mm_account_reclaimed_pages() */ #include #include #include @@ -2063,8 +2063,7 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab) /* Make the mapping reset visible before clearing the flag */ smp_wmb(); __folio_clear_slab(folio); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += pages; + mm_account_reclaimed_pages(pages); unaccount_slab(slab, order, s); __free_pages(&folio->page, order); } diff --git a/mm/vmscan.c b/mm/vmscan.c index c82bd89f90364..049e39202e6ce 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -188,18 +188,6 @@ struct scan_control { */ int vm_swappiness = 60; -static void set_task_reclaim_state(struct task_struct *task, - struct reclaim_state *rs) -{ - /* Check for an overwrite */ - WARN_ON_ONCE(rs && task->reclaim_state); - - /* Check for the nulling of an already-nulled member */ - WARN_ON_ONCE(!rs && !task->reclaim_state); - - task->reclaim_state = rs; -} - LIST_HEAD(shrinker_list); DECLARE_RWSEM(shrinker_rwsem); @@ -511,6 +499,59 @@ static bool writeback_throttling_sane(struct scan_control *sc) } #endif +static void set_task_reclaim_state(struct task_struct *task, + struct reclaim_state *rs) +{ + /* Check for an overwrite */ + WARN_ON_ONCE(rs && task->reclaim_state); + + /* Check for the nulling of an already-nulled member */ + WARN_ON_ONCE(!rs && !task->reclaim_state); + + task->reclaim_state = rs; +} + +/* + * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to + * scan_control->nr_reclaimed. + */ +static void flush_reclaim_state(struct scan_control *sc, + struct reclaim_state *rs) +{ + /* + * Currently, reclaim_state->reclaimed includes three types of pages + * freed outside of vmscan: + * (1) Slab pages. + * (2) Clean file pages from pruned inodes. + * (3) XFS freed buffer pages. + * + * For all of these cases, we have no way of finding out whether these + * pages were related to the memcg under reclaim. For example, a freed + * slab page could have had only a single object charged to the memcg + * under reclaim. Also, populated inodes are not on shrinker LRUs + * anymore except on highmem systems. + * + * Instead of over-reporting the reclaimed pages in a memcg reclaim, + * only count such pages in global reclaim. This prevents unnecessary + * retries during memcg charging and false positive from proactive + * reclaim (memory.reclaim). + * + * For uncommon cases were the freed pages were actually significantly + * charged to the memcg under reclaim, and we end up under-reporting, it + * should be fine. The freed pages will be uncharged anyway, even if + * they are not reported properly, and we will be able to make forward + * progress in charging (which is usually in a retry loop). + * + * We can go one step further, and report the uncharged objcg pages in + * memcg reclaim, to make reporting more accurate and reduce + * under-reporting, but it's probably not worth the complexity for now. + */ + if (rs && global_reclaim(sc)) { + sc->nr_reclaimed += rs->reclaimed; + rs->reclaimed = 0; + } +} + static long xchg_nr_deferred(struct shrinker *shrinker, struct shrink_control *sc) { @@ -5346,10 +5387,7 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned, sc->nr_reclaimed - reclaimed); - if (global_reclaim(sc)) { - sc->nr_reclaimed += current->reclaim_state->reclaimed_slab; - current->reclaim_state->reclaimed_slab = 0; - } + flush_reclaim_state(sc, current->reclaim_state); return success ? MEMCG_LRU_YOUNG : 0; } @@ -6474,10 +6512,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) shrink_node_memcgs(pgdat, sc); - if (reclaim_state && global_reclaim(sc)) { - sc->nr_reclaimed += reclaim_state->reclaimed_slab; - reclaim_state->reclaimed_slab = 0; - } + flush_reclaim_state(sc, reclaim_state); /* Record the subtree's reclaim efficiency */ if (!sc->proactive)