2022-11-10 11:43:01

by Chao Xu

Subject: [PATCH v1] mm/vmscan: simplify the nr assignment logic for pages to scan

By default the assignment logic of anonymouns or file inactive
pages and active pages to scan using the same duplicated code
snippet. To simplify the logic, merge the same part.

Signed-off-by: Chao Xu <[email protected]>
---
mm/vmscan.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 04d8b88e5216..69e458e51c81 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5932,14 +5932,11 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
* scan target and the percentage scanning already complete
*/
lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
- nr_scanned = targets[lru] - nr[lru];
- nr[lru] = targets[lru] * (100 - percentage) / 100;
- nr[lru] -= min(nr[lru], nr_scanned);
-
- lru += LRU_ACTIVE;
- nr_scanned = targets[lru] - nr[lru];
- nr[lru] = targets[lru] * (100 - percentage) / 100;
- nr[lru] -= min(nr[lru], nr_scanned);
+ for ( ; lru <= lru + LRU_ACTIVE; lru += LRU_ACTIVE) {
+ nr_scanned = targets[lru] - nr[lru];
+ nr[lru] = targets[lru] * (100 - percentage) / 100;
+ nr[lru] -= min(nr[lru], nr_scanned);
+ }

scan_adjusted = true;
}
--
2.34.1

2022-11-17 18:27:35

by Johannes Weiner

Subject: Re: [PATCH v1] mm/vmscan: simplify the nr assignment logic for pages to scan

On Thu, Nov 10, 2022 at 07:31:30PM +0800, Chao Xu wrote:
> By default the assignment logic of anonymouns or file inactive
> pages and active pages to scan using the same duplicated code
> snippet. To simplify the logic, merge the same part.
>
> Signed-off-by: Chao Xu <[email protected]>
> ---
> mm/vmscan.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 04d8b88e5216..69e458e51c81 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -5932,14 +5932,11 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
> * scan target and the percentage scanning already complete
> */
> lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
> - nr_scanned = targets[lru] - nr[lru];
> - nr[lru] = targets[lru] * (100 - percentage) / 100;
> - nr[lru] -= min(nr[lru], nr_scanned);
> -
> - lru += LRU_ACTIVE;
> - nr_scanned = targets[lru] - nr[lru];
> - nr[lru] = targets[lru] * (100 - percentage) / 100;
> - nr[lru] -= min(nr[lru], nr_scanned);
> + for ( ; lru <= lru + LRU_ACTIVE; lru += LRU_ACTIVE) {

As Yu points out, this will loop until lru overflows.

NAK.