* Re: [PATCH] fs: drop_caches: draining pages before dropping caches
[not found] <20230630092203.16080-1-andrew.yang@mediatek.com>
@ 2023-07-03 10:16 ` Christian Brauner
2023-07-04 18:06 ` Andrew Morton
1 sibling, 0 replies; 2+ messages in thread
From: Christian Brauner @ 2023-07-03 10:16 UTC (permalink / raw)
To: Andrew Yang, linux-mm
Cc: Alexander Viro, Matthias Brugger, AngeloGioacchino Del Regno,
wsd_upstream, casper.li, linux-fsdevel, linux-kernel,
linux-arm-kernel, linux-mediatek, Matthew Wilcox
Really more suitable for -mm to review.
On Fri, Jun 30, 2023 at 05:22:02PM +0800, Andrew Yang wrote:
> We expect a file page access after dropping caches should be a major
> fault, but sometimes it's still a minor fault. That's because a file
> page can't be dropped if it's in a per-cpu pagevec. Draining all pages
> from per-cpu pagevec to lru list before trying to drop caches.
>
> Signed-off-by: Andrew Yang <andrew.yang@mediatek.com>
> ---
> fs/drop_caches.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/drop_caches.c b/fs/drop_caches.c
> index e619c31b6bd9..b9575957a7c2 100644
> --- a/fs/drop_caches.c
> +++ b/fs/drop_caches.c
> @@ -10,6 +10,7 @@
> #include <linux/writeback.h>
> #include <linux/sysctl.h>
> #include <linux/gfp.h>
> +#include <linux/swap.h>
> #include "internal.h"
>
> /* A global variable is a bit ugly, but it keeps the code simple */
> @@ -59,6 +60,7 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
> static int stfu;
>
> if (sysctl_drop_caches & 1) {
> + lru_add_drain_all();
> iterate_supers(drop_pagecache_sb, NULL);
> count_vm_event(DROP_PAGECACHE);
> }
> --
> 2.18.0
>
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH] fs: drop_caches: draining pages before dropping caches
[not found] <20230630092203.16080-1-andrew.yang@mediatek.com>
2023-07-03 10:16 ` [PATCH] fs: drop_caches: draining pages before dropping caches Christian Brauner
@ 2023-07-04 18:06 ` Andrew Morton
1 sibling, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2023-07-04 18:06 UTC (permalink / raw)
To: Andrew Yang
Cc: Alexander Viro, Christian Brauner, Matthias Brugger,
AngeloGioacchino Del Regno, wsd_upstream, casper.li,
linux-fsdevel, linux-kernel, linux-arm-kernel, linux-mediatek,
linux-mm
On Fri, 30 Jun 2023 17:22:02 +0800 Andrew Yang <andrew.yang@mediatek.com> wrote:
> We expect a file page access after dropping caches should be a major
> fault, but sometimes it's still a minor fault. That's because a file
> page can't be dropped if it's in a per-cpu pagevec. Draining all pages
> from per-cpu pagevec to lru list before trying to drop caches.
>
> --- a/fs/drop_caches.c
> +++ b/fs/drop_caches.c
> @@ -10,6 +10,7 @@
> #include <linux/writeback.h>
> #include <linux/sysctl.h>
> #include <linux/gfp.h>
> +#include <linux/swap.h>
> #include "internal.h"
>
> /* A global variable is a bit ugly, but it keeps the code simple */
> @@ -59,6 +60,7 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
> static int stfu;
>
> if (sysctl_drop_caches & 1) {
> + lru_add_drain_all();
> iterate_supers(drop_pagecache_sb, NULL);
> count_vm_event(DROP_PAGECACHE);
> }
um, yes. I'm suprised that this oversight has survived 20+ years.
^ permalink raw reply [flat|nested] 2+ messages in thread