mm/vmscan.c: refactor shrink_node()

This patch refactors shrink_node() to improve readability for the upcoming
changes to mm/vmscan.c.

Link: https://lkml.kernel.org/r/20220918080010.2920238-4-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Acked-by: Steven Barrett <steven@liquorix.net>
Acked-by: Suleiman Souhlal <suleiman@google.com>
Tested-by: Daniel Byrne <djbyrne@mtu.edu>
Tested-by: Donald Carr <d@chaos-reins.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
Tested-by: Shuang Zhai <szhai2@cs.rochester.edu>
Tested-by: Sofia Trinh <sofia.trinh@edi.works>
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michael Larabel <Michael@MichaelLarabel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c879694..9c77df1 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2728,6 +2728,109 @@ enum scan_balance {
        SCAN_FILE,
 };
 
+static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc)
+{
+       unsigned long file;
+       struct lruvec *target_lruvec;
+
+       target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
+
+       /*
+        * Flush the memory cgroup stats, so that we read accurate per-memcg
+        * lruvec stats for heuristics.
+        */
+       mem_cgroup_flush_stats();
+
+       /*
+        * Determine the scan balance between anon and file LRUs.
+        */
+       spin_lock_irq(&target_lruvec->lru_lock);
+       sc->anon_cost = target_lruvec->anon_cost;
+       sc->file_cost = target_lruvec->file_cost;
+       spin_unlock_irq(&target_lruvec->lru_lock);
+
+       /*
+        * Target desirable inactive:active list ratios for the anon
+        * and file LRU lists.
+        */
+       if (!sc->force_deactivate) {
+               unsigned long refaults;
+
+               /*
+                * When refaults are being observed, it means a new
+                * workingset is being established. Deactivate to get
+                * rid of any stale active pages quickly.
+                */
+               refaults = lruvec_page_state(target_lruvec,
+                               WORKINGSET_ACTIVATE_ANON);
+               if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
+                       inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
+                       sc->may_deactivate |= DEACTIVATE_ANON;
+               else
+                       sc->may_deactivate &= ~DEACTIVATE_ANON;
+
+               refaults = lruvec_page_state(target_lruvec,
+                               WORKINGSET_ACTIVATE_FILE);
+               if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
+                   inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
+                       sc->may_deactivate |= DEACTIVATE_FILE;
+               else
+                       sc->may_deactivate &= ~DEACTIVATE_FILE;
+       } else
+               sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
+
+       /*
+        * If we have plenty of inactive file pages that aren't
+        * thrashing, try to reclaim those first before touching
+        * anonymous pages.
+        */
+       file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
+       if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
+               sc->cache_trim_mode = 1;
+       else
+               sc->cache_trim_mode = 0;
+
+       /*
+        * Prevent the reclaimer from falling into the cache trap: as
+        * cache pages start out inactive, every cache fault will tip
+        * the scan balance towards the file LRU.  And as the file LRU
+        * shrinks, so does the window for rotation from references.
+        * This means we have a runaway feedback loop where a tiny
+        * thrashing file LRU becomes infinitely more attractive than
+        * anon pages.  Try to detect this based on file LRU size.
+        */
+       if (!cgroup_reclaim(sc)) {
+               unsigned long total_high_wmark = 0;
+               unsigned long free, anon;
+               int z;
+
+               free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
+               file = node_page_state(pgdat, NR_ACTIVE_FILE) +
+                          node_page_state(pgdat, NR_INACTIVE_FILE);
+
+               for (z = 0; z < MAX_NR_ZONES; z++) {
+                       struct zone *zone = &pgdat->node_zones[z];
+
+                       if (!managed_zone(zone))
+                               continue;
+
+                       total_high_wmark += high_wmark_pages(zone);
+               }
+
+               /*
+                * Consider anon: if that's low too, this isn't a
+                * runaway file reclaim problem, but rather just
+                * extreme pressure. Reclaim as per usual then.
+                */
+               anon = node_page_state(pgdat, NR_INACTIVE_ANON);
+
+               sc->file_is_tiny =
+                       file + free <= total_high_wmark &&
+                       !(sc->may_deactivate & DEACTIVATE_ANON) &&
+                       anon >> sc->priority;
+       }
+}
+
 /*
  * Determine how aggressively the anon and file LRU lists should be
  * scanned.
@@ -3197,109 +3300,16 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
        unsigned long nr_reclaimed, nr_scanned;
        struct lruvec *target_lruvec;
        bool reclaimable = false;
-       unsigned long file;
 
        target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
 
 again:
-       /*
-        * Flush the memory cgroup stats, so that we read accurate per-memcg
-        * lruvec stats for heuristics.
-        */
-       mem_cgroup_flush_stats();
-
        memset(&sc->nr, 0, sizeof(sc->nr));
 
        nr_reclaimed = sc->nr_reclaimed;
        nr_scanned = sc->nr_scanned;
 
-       /*
-        * Determine the scan balance between anon and file LRUs.
-        */
-       spin_lock_irq(&target_lruvec->lru_lock);
-       sc->anon_cost = target_lruvec->anon_cost;
-       sc->file_cost = target_lruvec->file_cost;
-       spin_unlock_irq(&target_lruvec->lru_lock);
-
-       /*
-        * Target desirable inactive:active list ratios for the anon
-        * and file LRU lists.
-        */
-       if (!sc->force_deactivate) {
-               unsigned long refaults;
-
-               /*
-                * When refaults are being observed, it means a new
-                * workingset is being established. Deactivate to get
-                * rid of any stale active pages quickly.
-                */
-               refaults = lruvec_page_state(target_lruvec,
-                               WORKINGSET_ACTIVATE_ANON);
-               if (refaults != target_lruvec->refaults[WORKINGSET_ANON] ||
-                       inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
-                       sc->may_deactivate |= DEACTIVATE_ANON;
-               else
-                       sc->may_deactivate &= ~DEACTIVATE_ANON;
-
-               refaults = lruvec_page_state(target_lruvec,
-                               WORKINGSET_ACTIVATE_FILE);
-               if (refaults != target_lruvec->refaults[WORKINGSET_FILE] ||
-                   inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
-                       sc->may_deactivate |= DEACTIVATE_FILE;
-               else
-                       sc->may_deactivate &= ~DEACTIVATE_FILE;
-       } else
-               sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
-
-       /*
-        * If we have plenty of inactive file pages that aren't
-        * thrashing, try to reclaim those first before touching
-        * anonymous pages.
-        */
-       file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
-       if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
-               sc->cache_trim_mode = 1;
-       else
-               sc->cache_trim_mode = 0;
-
-       /*
-        * Prevent the reclaimer from falling into the cache trap: as
-        * cache pages start out inactive, every cache fault will tip
-        * the scan balance towards the file LRU.  And as the file LRU
-        * shrinks, so does the window for rotation from references.
-        * This means we have a runaway feedback loop where a tiny
-        * thrashing file LRU becomes infinitely more attractive than
-        * anon pages.  Try to detect this based on file LRU size.
-        */
-       if (!cgroup_reclaim(sc)) {
-               unsigned long total_high_wmark = 0;
-               unsigned long free, anon;
-               int z;
-
-               free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
-               file = node_page_state(pgdat, NR_ACTIVE_FILE) +
-                          node_page_state(pgdat, NR_INACTIVE_FILE);
-
-               for (z = 0; z < MAX_NR_ZONES; z++) {
-                       struct zone *zone = &pgdat->node_zones[z];
-                       if (!managed_zone(zone))
-                               continue;
-
-                       total_high_wmark += high_wmark_pages(zone);
-               }
-
-               /*
-                * Consider anon: if that's low too, this isn't a
-                * runaway file reclaim problem, but rather just
-                * extreme pressure. Reclaim as per usual then.
-                */
-               anon = node_page_state(pgdat, NR_INACTIVE_ANON);
-
-               sc->file_is_tiny =
-                       file + free <= total_high_wmark &&
-                       !(sc->may_deactivate & DEACTIVATE_ANON) &&
-                       anon >> sc->priority;
-       }
+       prepare_scan_count(pgdat, sc);
 
        shrink_node_memcgs(pgdat, sc);