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Message-ID: <20250718024134.1304745-1-ye.liu@linux.dev>
Date: Fri, 18 Jul 2025 10:41:32 +0800
From: Ye Liu <ye.liu@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>,
Davidlohr Bueso <dave@...olabs.net>,
"Paul E. McKenney" <paulmck@...nel.org>,
Josh Triplett <josh@...htriplett.org>,
Frederic Weisbecker <frederic@...nel.org>,
Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
Joel Fernandes <joelagnelf@...dia.com>,
Boqun Feng <boqun.feng@...il.com>,
Uladzislau Rezki <urezki@...il.com>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Ye Liu <liuye@...inos.cn>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Mike Rapoport <rppt@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Michal Hocko <mhocko@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Zqiang <qiang.zhang@...ux.dev>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Ben Segall <bsegall@...gle.com>,
Mel Gorman <mgorman@...e.de>,
Valentin Schneider <vschneid@...hat.com>,
Zi Yan <ziy@...dia.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Nico Pache <npache@...hat.com>,
Ryan Roberts <ryan.roberts@....com>,
Dev Jain <dev.jain@....com>,
Barry Song <baohua@...nel.org>,
Kemeng Shi <shikemeng@...weicloud.com>,
Kairui Song <kasong@...cent.com>,
Nhat Pham <nphamcs@...il.com>,
Baoquan He <bhe@...hat.com>,
Chris Li <chrisl@...nel.org>,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
rcu@...r.kernel.org
Subject: [PATCH] mm: Replace (20 - PAGE_SHIFT) with common macros for pages<->MB conversion
From: Ye Liu <liuye@...inos.cn>
Replace repeated (20 - PAGE_SHIFT) calculations with standard macros:
- MB_TO_PAGES(mb) converts MB to page count
- PAGES_TO_MB(pages) converts pages to MB
No functional change.
Signed-off-by: Ye Liu <liuye@...inos.cn>
---
include/linux/mm.h | 9 +++++++++
kernel/rcu/rcuscale.c | 2 +-
kernel/sched/fair.c | 5 ++---
mm/backing-dev.c | 2 +-
mm/huge_memory.c | 2 +-
mm/swap.c | 2 +-
6 files changed, 15 insertions(+), 7 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 957acde6ae62..0c1b2c074142 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -69,6 +69,15 @@ static inline void totalram_pages_add(long count)
extern void * high_memory;
+/*
+ * Convert between pages and MB
+ * 20 is the shift for 1MB (2^20 = 1MB)
+ * PAGE_SHIFT is the shift for page size (e.g., 12 for 4KB pages)
+ * So (20 - PAGE_SHIFT) converts between pages and MB
+ */
+#define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
+#define MB_TO_PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
+
#ifdef CONFIG_SYSCTL
extern int sysctl_legacy_va_layout;
#else
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index b521d0455992..7484d8ad5767 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -796,7 +796,7 @@ kfree_scale_thread(void *arg)
pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\n",
(unsigned long long)(end_time - start_time), kfree_loops,
rcuscale_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
- (mem_begin - mem_during) >> (20 - PAGE_SHIFT));
+ PAGES_TO_MB(mem_begin - mem_during));
if (shutdown) {
smp_mb(); /* Assign before wake. */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b9b4bbbf0af6..ae1d9a7ef202 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1489,7 +1489,7 @@ static unsigned int task_nr_scan_windows(struct task_struct *p)
* by the PTE scanner and NUMA hinting faults should be trapped based
* on resident pages
*/
- nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
+ nr_scan_pages = MB_TO_PAGES(sysctl_numa_balancing_scan_size);
rss = get_mm_rss(p->mm);
if (!rss)
rss = nr_scan_pages;
@@ -1926,8 +1926,7 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio,
}
def_th = sysctl_numa_balancing_hot_threshold;
- rate_limit = sysctl_numa_balancing_promote_rate_limit << \
- (20 - PAGE_SHIFT);
+ rate_limit = MB_TO_PAGES(sysctl_numa_balancing_promote_rate_limit);
numa_promotion_adjust_threshold(pgdat, rate_limit, def_th);
th = pgdat->nbp_threshold ? : def_th;
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 783904d8c5ef..e4d578e6121c 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -510,7 +510,7 @@ static void wb_update_bandwidth_workfn(struct work_struct *work)
/*
* Initial write bandwidth: 100 MB/s
*/
-#define INIT_BW (100 << (20 - PAGE_SHIFT))
+#define INIT_BW MB_TO_PAGES(100)
static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
gfp_t gfp)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 389620c65a5f..dcc33d9c300f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -911,7 +911,7 @@ static int __init hugepage_init(void)
* where the extra memory used could hurt more than TLB overhead
* is likely to save. The admin can still enable it through /sys.
*/
- if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
+ if (totalram_pages() < MB_TO_PAGES(512)) {
transparent_hugepage_flags = 0;
return 0;
}
diff --git a/mm/swap.c b/mm/swap.c
index 3632dd061beb..cb164f9ef9e3 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -1096,7 +1096,7 @@ static const struct ctl_table swap_sysctl_table[] = {
*/
void __init swap_setup(void)
{
- unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
+ unsigned long megs = PAGES_TO_MB(totalram_pages());
/* Use a smaller cluster for small-memory machines */
if (megs < 16)
--
2.43.0
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