On Fri, Jul 18, 2025 at 10:41:32AM +0800, Ye Liu wrote: > From: Ye Liu <[email protected]> > > 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 <[email protected]>
Nice idea :) NOte I see arch/x86/include/asm/pgtable.h has a pages_to_mb() static inline declaration, but probably being an asm include can't ref mm.h so meh not a big deal. LGTM, so: Reviewed-by: Lorenzo Stoakes <[email protected]> > --- > 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 >
