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SubjectRe: [PATCH v2 1/3] vmscan,memcg: memcg aware swap token
On Thu, 19 May 2011 11:30:53 +0900
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> Currently, memcg reclaim can disable swap token even if the swap token
> mm doesn't belong in its memory cgroup. It's slightly risky. If an
> admin creates very small mem-cgroup and silly guy runs contentious heavy
> memory pressure workload, every tasks are going to lose swap token and
> then system may become unresponsive. That's bad.
>
> This patch adds 'memcg' parameter into disable_swap_token(). and if
> the parameter doesn't match swap token, VM doesn't disable it.
>
>
> ...
>
> --- a/mm/thrash.c
> +++ b/mm/thrash.c
> @@ -21,14 +21,17 @@
> #include <linux/mm.h>
> #include <linux/sched.h>
> #include <linux/swap.h>
> +#include <linux/memcontrol.h>
>
> static DEFINE_SPINLOCK(swap_token_lock);
> struct mm_struct *swap_token_mm;
> +struct mem_cgroup *swap_token_memcg;
> static unsigned int global_faults;
>
> void grab_swap_token(struct mm_struct *mm)
> {
> int current_interval;
> + struct mem_cgroup *memcg;
>
> global_faults++;
>
> @@ -38,40 +41,72 @@ void grab_swap_token(struct mm_struct *mm)
> return;
>
> /* First come first served */
> - if (swap_token_mm == NULL) {
> - mm->token_priority = mm->token_priority + 2;
> - swap_token_mm = mm;
> + if (!swap_token_mm)
> + goto replace_token;
> +
> + if (mm == swap_token_mm) {
> + mm->token_priority += 2;
> goto out;
> }
>
> - if (mm != swap_token_mm) {
> - if (current_interval < mm->last_interval)
> - mm->token_priority++;
> - else {
> - if (likely(mm->token_priority > 0))
> - mm->token_priority--;
> - }
> - /* Check if we deserve the token */
> - if (mm->token_priority > swap_token_mm->token_priority) {
> - mm->token_priority += 2;
> - swap_token_mm = mm;
> - }
> - } else {
> - /* Token holder came in again! */
> - mm->token_priority += 2;
> + if (current_interval < mm->last_interval)
> + mm->token_priority++;
> + else {
> + if (likely(mm->token_priority > 0))
> + mm->token_priority--;
> }
>
> + /* Check if we deserve the token */
> + if (mm->token_priority > swap_token_mm->token_priority)
> + goto replace_token;
> +
> out:
> mm->faultstamp = global_faults;
> mm->last_interval = current_interval;
> spin_unlock(&swap_token_lock);
> + return;
> +
> +replace_token:
> + mm->token_priority += 2;
> + memcg = try_get_mem_cgroup_from_mm(mm);
> + if (memcg)
> + css_put(mem_cgroup_css(memcg));
> + swap_token_mm = mm;
> + swap_token_memcg = memcg;
> + goto out;
> }

CONFIG_CGROUPS=n:

mm/thrash.c: In function 'grab_swap_token':
mm/thrash.c:73: error: implicit declaration of function 'css_put'

I don't think that adding a null stub for css_put() is the right fix
here...


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