Commit d0966120 authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Andrew Morton
Browse files

vmalloc: align nr_vmalloc_pages and vmap_lazy_nr 

Currently both atomics share one cache-line:

<snip>
...
ffffffff83eab400 b vmap_lazy_nr
ffffffff83eab408 b nr_vmalloc_pages
...
<snip>

those are global variables and they are only 8 bytes apart.  Since they
are modified by different threads this causes a false sharing.  This can
lead to a performance drop due to unnecessary cache invalidations.

After this patch it is aligned to a cache line boundary:

<snip>
...
ffffffff8260a600 d vmap_lazy_nr
ffffffff8260a640 d nr_vmalloc_pages
...
<snip>

Link: https://lkml.kernel.org/r/20250417161216.88318-4-urezki@gmail.com


Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: default avatarBaoquan He <bhe@redhat.com>
Reviewed-by: default avatarAdrian Huang <ahuang12@lenovo.com>
Tested-by: default avatarAdrian Huang <ahuang12@lenovo.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Christop Hellwig <hch@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7a6fe587

mm/vmalloc.c

+2 −3
Original line number Diff line number Diff line
@@ -1008,7 +1008,8 @@ static BLOCKING_NOTIFIER_HEAD(vmap_notify_list); 
static void drain_vmap_area_work(struct work_struct *work);

static DECLARE_WORK(drain_vmap_work, drain_vmap_area_work);



static atomic_long_t nr_vmalloc_pages;

static __cacheline_aligned_in_smp atomic_long_t nr_vmalloc_pages;

static __cacheline_aligned_in_smp atomic_long_t vmap_lazy_nr;



unsigned long vmalloc_nr_pages(void)

{
@@ -2117,8 +2118,6 @@ static unsigned long lazy_max_pages(void) 
	return log * (32UL * 1024 * 1024 / PAGE_SIZE);

}



static atomic_long_t vmap_lazy_nr = ATOMIC_LONG_INIT(0);



/*

 * Serialize vmap purging.  There is no actual critical section protected

 * by this lock, but we want to avoid concurrent calls for performance