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Fri, 19 Sep 2025 12:52:25 -0700 (PDT) From: Joshua Hahn To: Andrew Morton , Johannes Weiner Cc: Chris Mason , Kiryl Shutsemau , "Liam R. Howlett" , Brendan Jackman , David Hildenbrand , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: [PATCH 1/4] mm/page_alloc/vmstat: Simplify refresh_cpu_vm_stats change detection Date: Fri, 19 Sep 2025 12:52:19 -0700 Message-ID: <20250919195223.1560636-2-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250919195223.1560636-1-joshua.hahnjy@gmail.com> References: <20250919195223.1560636-1-joshua.hahnjy@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 10F2C14000B X-Stat-Signature: 4ckhiroekr1ki6ks46f87f89wyux93qh X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758311546-18326 X-HE-Meta: U2FsdGVkX18MxvqUO6EXnZRD61fOazyARbMmn6yYqc22xFPpKMiE7YehWanxrqRNwZ8waTJb3Ys3o/yNL6JNeZmLBXsnkKJl5S/URSHfbSw1jC3aa4fyGbsm00w2X76suGlg0Um4LchHavlrraLLzfNkqkYSd9Tntb26C+0mYlcsXjUXbCIoxkiwJv0HuMsGSz0Loovok+dzsyk0IyLtVuyXuKKFw4yQ7UeLCnZUexC74uktzzHLmIG4GJ/6pBAc8UuRCOIScx89PSIyNYpUbkGO/SS+WoLycuO4sr/wIgdQ4XFf2bUrNMsHQ8LSS/zCZVLNqn5TlM7rG/sAMCO4+CJWXgcFE6UQ9BNludwKaRDtYYYS0xhxTYt2CeVjn2p4I9PQgUDTtqu4hokH/fciyZoElt+JbP5GKDzkM1yaDwTbOvHo5bFbSgnG0/9hDTd9GJDXEqdX4KT4T+OE32GMK5hlwXPAvsWkU67r2i42t/kQPqRLJTS99LPuUqB4P3VIA2Oq2Kcuib9LGU2GNFcBuex6Xrl0hjRDhiJOhgJkT7SNvl+kAIKDt4GjXi6+VeO+FTNn/FstaeQQzsC17YEB/SqklkTnHlHQEMxpH7frY/HzzDQX31gUO7Wu5Ufy1T0OGKz5ouaFD2VGfUmIQ2lQDjRx32cW95BantlICjeAMeR7oQbgHKzUxdYcXxTZB1na9JHlSThtfnaTwY56KAb2OQmGrQRK2Bso+6da8mYQKpLswk3hMXBuzok8h6ySIzzisYDt2z7ykQ7x0lFtS4RKyvvUAComYdY0m4lQj1jbgao5XqlPo4ZMYBbHrPcu5vsJ3v8/2p9kIF0JwG1nTOuYVYGtpjJcEj56BAmLzmUvsHZUZfJ0EJSev6Z3mhndEd1C9/DLmsQ3HTlIbsoMeda6TgnOXsMoTE5er3VU3xNutOst4Pz0xdSHPGA7rjclMyhZxt49YsbGy938hNmxXST N8X6V8Ff 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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: List-Subscribe: List-Unsubscribe: Currently, refresh_cpu_vm_stats returns an int, indicating how many changes were made during its updates. Using this information, callers like vmstat_update can heuristically determine if more work will be done in the future. However, all of refresh_cpu_vm_stats's callers either (a) ignore the result, only caring about performing the updates, or (b) only care about whether changes were made, but not *how many* changes were made. Simplify the code by returning a bool instead to indicate if updates were made. In addition, simplify fold_diff and decay_pcp_high to return a bool for the same reason. Signed-off-by: Joshua Hahn --- include/linux/gfp.h | 2 +- mm/page_alloc.c | 8 ++++---- mm/vmstat.c | 26 +++++++++++++------------- 3 files changed, 18 insertions(+), 18 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 5ebf26fcdcfa..63c72cb1d117 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -386,7 +386,7 @@ extern void free_pages(unsigned long addr, unsigned int order); #define free_page(addr) free_pages((addr), 0) void page_alloc_init_cpuhp(void); -int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp); +bool decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp); void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp); void drain_all_pages(struct zone *zone); void drain_local_pages(struct zone *zone); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d1d037f97c5f..77e7d9a5f149 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2561,10 +2561,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, * Called from the vmstat counter updater to decay the PCP high. * Return whether there are addition works to do. */ -int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp) +bool decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp) { int high_min, to_drain, batch; - int todo = 0; + bool todo; high_min = READ_ONCE(pcp->high_min); batch = READ_ONCE(pcp->batch); @@ -2577,7 +2577,7 @@ int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp) pcp->high = max3(pcp->count - (batch << CONFIG_PCP_BATCH_SCALE_MAX), pcp->high - (pcp->high >> 3), high_min); if (pcp->high > high_min) - todo++; + todo = true; } to_drain = pcp->count - pcp->high; @@ -2585,7 +2585,7 @@ int decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp) spin_lock(&pcp->lock); free_pcppages_bulk(zone, to_drain, pcp, 0); spin_unlock(&pcp->lock); - todo++; + todo = true; } return todo; diff --git a/mm/vmstat.c b/mm/vmstat.c index 71cd1ceba191..1f74a3517ab2 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -771,25 +771,25 @@ EXPORT_SYMBOL(dec_node_page_state); /* * Fold a differential into the global counters. - * Returns the number of counters updated. + * Returns whether counters were updated. */ static int fold_diff(int *zone_diff, int *node_diff) { int i; - int changes = 0; + bool changed = false; for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) if (zone_diff[i]) { atomic_long_add(zone_diff[i], &vm_zone_stat[i]); - changes++; + changed = true; } for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) if (node_diff[i]) { atomic_long_add(node_diff[i], &vm_node_stat[i]); - changes++; + changed = true; } - return changes; + return changed; } /* @@ -806,16 +806,16 @@ static int fold_diff(int *zone_diff, int *node_diff) * with the global counters. These could cause remote node cache line * bouncing and will have to be only done when necessary. * - * The function returns the number of global counters updated. + * The function returns whether global counters were updated. */ -static int refresh_cpu_vm_stats(bool do_pagesets) +static bool refresh_cpu_vm_stats(bool do_pagesets) { struct pglist_data *pgdat; struct zone *zone; int i; int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, }; int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, }; - int changes = 0; + bool changed = false; for_each_populated_zone(zone) { struct per_cpu_zonestat __percpu *pzstats = zone->per_cpu_zonestats; @@ -839,7 +839,7 @@ static int refresh_cpu_vm_stats(bool do_pagesets) if (do_pagesets) { cond_resched(); - changes += decay_pcp_high(zone, this_cpu_ptr(pcp)); + changed |= decay_pcp_high(zone, this_cpu_ptr(pcp)); #ifdef CONFIG_NUMA /* * Deal with draining the remote pageset of this @@ -861,13 +861,13 @@ static int refresh_cpu_vm_stats(bool do_pagesets) } if (__this_cpu_dec_return(pcp->expire)) { - changes++; + changed = true; continue; } if (__this_cpu_read(pcp->count)) { drain_zone_pages(zone, this_cpu_ptr(pcp)); - changes++; + changed = true; } #endif } @@ -887,8 +887,8 @@ static int refresh_cpu_vm_stats(bool do_pagesets) } } - changes += fold_diff(global_zone_diff, global_node_diff); - return changes; + changed |= fold_diff(global_zone_diff, global_node_diff); + return changed; } /* -- 2.47.3