[PATCH] mm/damon: remove __read_mostly from memory_idle_ms_percentiles

[PATCH] mm/damon: remove __read_mostly from memory_idle_ms_percentiles

[lirongqing]

From: Li RongQing <lirongqing@baidu.com>

The 'memory_idle_ms_percentiles' array in DAMON_STAT is updated
frequently by the kernel to reflect the latest idle time statistics.
Marking it as '__read_mostly' is inappropriate for data that is
regularly written to, as it can lead to cache pollution in the
read-mostly section.

Remove the '__read_mostly' annotation to accurately reflect the
variable's usage pattern.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 mm/damon/stat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/damon/stat.c b/mm/damon/stat.c
index ed8e362..5c4eec0 100644
--- a/mm/damon/stat.c
+++ b/mm/damon/stat.c
@@ -34,7 +34,7 @@ module_param(estimated_memory_bandwidth, ulong, 0400);
 MODULE_PARM_DESC(estimated_memory_bandwidth,
 		"Estimated memory bandwidth usage in bytes per second");
 
-static long memory_idle_ms_percentiles[101] __read_mostly = {0,};
+static long memory_idle_ms_percentiles[101] = {0,};
 module_param_array(memory_idle_ms_percentiles, long, NULL, 0400);
 MODULE_PARM_DESC(memory_idle_ms_percentiles,
 		"Memory idle time percentiles in milliseconds");
-- 
2.9.4

Re: [PATCH] mm/damon: remove __read_mostly from memory_idle_ms_percentiles

[SeongJae Park]

On Fri, 30 Jan 2026 03:56:03 -0500 lirongqing <lirongqing@baidu.com> wrote:

> From: Li RongQing <lirongqing@baidu.com>
> 
> The 'memory_idle_ms_percentiles' array in DAMON_STAT is updated
> frequently by the kernel to reflect the latest idle time statistics.
> Marking it as '__read_mostly' is inappropriate for data that is
> regularly written to, as it can lead to cache pollution in the
> read-mostly section.
> 
> Remove the '__read_mostly' annotation to accurately reflect the
> variable's usage pattern.

Nice catch, thank you Li!

> 
> Signed-off-by: Li RongQing <lirongqing@baidu.com>

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

[...]

Re: [PATCH] mm/damon: remove __read_mostly from memory_idle_ms_percentiles

[SeongJae Park]

One nit.  Let's use "mm/damon/stat:" for the subject prefix.  Andrew, could you
please make the change when you add this to mm-new?


Thanks,
SJ

[...]