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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49508732395sm74727475e9.5.2026.07.14.06.23.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jul 2026 06:23:02 -0700 (PDT) From: Petr Tesarik To: Andrew Morton , Vlastimil Babka , Johannes Weiner , Zi Yan , linux-mm@kvack.org Cc: David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , linux-kernel@vger.kernel.org, Petr Tesarik Subject: [PATCH v4 1/1] mm: let node_reclaim() return the number of pages reclaimed Date: Tue, 14 Jul 2026 15:23:00 +0200 Message-ID: <20260714132300.2136018-1-ptesarik@suse.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit There is only one caller, get_page_from_freelist(), and it does not make any use of the reason for skipping the reclaim, nor does it make any distinction between a full and partially successful reclaim. Therefore, node_reclaim() can simply return the number of pages that have been reclaimed, same as __node_reclaim(), and the NODE_RECLAIM_xxx macros can be removed. There is one small change of behavior when __node_reclaim() was attempted but returned zero. The allocation now skips the zone immediately; before this patch, the zone watermarks were checked first. I believe it was an oversight rather than intention, because the chances that zone watermark is OK after __node_reclaim() did not reclaim any pages are very close to zero. Originally, I was looking for occurences of NODE_RECLAIM_SOME and NODE_RECLAIM_SUCCESS, but I couldn't find any. That's because they are typecast from the result of a relational operator. This seemed a bit fragile, so I dug a bit deeper and came up with this proposed cleanup. Signed-off-by: Petr Tesarik Reviewed-by: Vlastimil Babka (SUSE) Reviewed-by: Zi Yan Acked-by: Johannes Weiner -- Changes from v3: - remove NODE_RECLAIM_xxx macro #define's Changes from v2: - remove the enum and return the number of pages reclaimed Changes from v1: - use an enum instead of a bool --- mm/internal.h | 14 +++++--------- mm/page_alloc.c | 19 ++++--------------- mm/vmscan.c | 16 ++++++++-------- 3 files changed, 17 insertions(+), 32 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 874be94cf2570..f26423de4ca28 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1098,23 +1098,19 @@ static inline void mlock_drain_local(void) { } static inline void mlock_drain_remote(int cpu) { } #endif /* !CONFIG_MMU */ -#define NODE_RECLAIM_NOSCAN -2 -#define NODE_RECLAIM_FULL -1 -#define NODE_RECLAIM_SOME 0 -#define NODE_RECLAIM_SUCCESS 1 - #ifdef CONFIG_NUMA extern int node_reclaim_mode; -extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int); +extern unsigned long node_reclaim(struct pglist_data *pgdat, + gfp_t gfp_mask, unsigned int order); extern int find_next_best_node(int node, nodemask_t *used_node_mask); #else #define node_reclaim_mode 0 -static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask, - unsigned int order) +static inline unsigned long node_reclaim(struct pglist_data *pgdat, + gfp_t mask, unsigned int order) { - return NODE_RECLAIM_NOSCAN; + return 0; } static inline int find_next_best_node(int node, nodemask_t *used_node_mask) { diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9c97a86da2b9f..af63558391345 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3908,8 +3908,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, if (!zone_watermark_fast(zone, order, mark, ac->highest_zoneidx, alloc_flags, gfp_mask)) { - int ret; - if (cond_accept_memory(zone, order, alloc_flags)) goto try_this_zone; @@ -3930,22 +3928,13 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, !zone_allows_reclaim(zonelist_zone(ac->preferred_zoneref), zone)) continue; - ret = node_reclaim(zone->zone_pgdat, gfp_mask, order); - switch (ret) { - case NODE_RECLAIM_NOSCAN: - /* did not scan */ - continue; - case NODE_RECLAIM_FULL: - /* scanned but unreclaimable */ + if (!node_reclaim(zone->zone_pgdat, gfp_mask, order)) continue; - default: - /* did we reclaim enough */ - if (zone_watermark_ok(zone, order, mark, - ac->highest_zoneidx, alloc_flags)) - goto try_this_zone; + /* did we reclaim enough */ + if (!zone_watermark_ok(zone, order, mark, + ac->highest_zoneidx, alloc_flags)) continue; - } } try_this_zone: diff --git a/mm/vmscan.c b/mm/vmscan.c index 4357a44ee8767..b7ef032e78a0b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -7768,9 +7768,9 @@ static unsigned long __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, return sc->nr_reclaimed; } -int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) +unsigned long node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) { - int ret; + unsigned long ret; /* Minimum pages needed in order to stay on node */ const unsigned long nr_pages = 1 << order; struct scan_control sc = { @@ -7797,13 +7797,13 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages && node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <= pgdat->min_slab_pages) - return NODE_RECLAIM_FULL; + return 0; /* * Do not scan if the allocation should not be delayed. */ if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC)) - return NODE_RECLAIM_NOSCAN; + return 0; /* * Only run node reclaim on the local node or on nodes that do not @@ -7812,15 +7812,15 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) * as wide as possible. */ if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id()) - return NODE_RECLAIM_NOSCAN; + return 0; if (test_and_set_bit_lock(PGDAT_RECLAIM_LOCKED, &pgdat->flags)) - return NODE_RECLAIM_NOSCAN; + return 0; - ret = __node_reclaim(pgdat, gfp_mask, nr_pages, &sc) >= nr_pages; + ret = __node_reclaim(pgdat, gfp_mask, nr_pages, &sc); clear_bit_unlock(PGDAT_RECLAIM_LOCKED, &pgdat->flags); - if (ret) + if (ret >= nr_pages) count_vm_event(PGSCAN_ZONE_RECLAIM_SUCCESS); else count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); -- 2.54.0