In the cgroup v2 cpu subsystem, assuming we have a
cgroup named test, we set cpu.max and cpu.max.burst:
# echo 1000000 > /sys/fs/cgroup/test/cpu.max
# echo 1000000 > /sys/fs/cgroup/test/cpu.max.burst
then we check cpu.max and cpu.max.burst:
# cat /sys/fs/cgroup/test/cpu.max
1000000 100000
# cat /sys/fs/cgroup/test/cpu.max.burst
1000000
Next we set cpu.max again and check cpu.max and
cpu.max.burst:
# echo 2000000 > /sys/fs/cgroup/test/cpu.max
# cat /sys/fs/cgroup/test/cpu.max
2000000 100000
# cat /sys/fs/cgroup/test/cpu.max.burst
1000
we found that the cpu.max.burst value changed unexpectedly.
In cpu_max_write(), the unit of the burst value returned
by tg_get_cfs_burst() is microseconds, while in cpu_max_write(),
the burst unit used for calculation should be nanoseconds,
which leads to the bug.
To fix it, we get the burst value directly from
tg->cfs_bandwidth.burst.
Reported-by: Qixin Liao <[email protected]>
Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller")
Signed-off-by: Cheng Yu <[email protected]>
Signed-off-by: Zhang Qiao <[email protected]>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7019a40457a6..d211d40a2edc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11402,7 +11402,7 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of,
{
struct task_group *tg = css_tg(of_css(of));
u64 period = tg_get_cfs_period(tg);
- u64 burst = tg_get_cfs_burst(tg);
+ u64 burst = tg->cfs_bandwidth.burst;
u64 quota;
int ret;
--
2.25.1
On Wed, 24 Apr 2024 at 15:29, Cheng Yu <[email protected]> wrote:
>
> In the cgroup v2 cpu subsystem, assuming we have a
> cgroup named test, we set cpu.max and cpu.max.burst:
> # echo 1000000 > /sys/fs/cgroup/test/cpu.max
> # echo 1000000 > /sys/fs/cgroup/test/cpu.max.burst
> then we check cpu.max and cpu.max.burst:
> # cat /sys/fs/cgroup/test/cpu.max
> 1000000 100000
> # cat /sys/fs/cgroup/test/cpu.max.burst
> 1000000
>
> Next we set cpu.max again and check cpu.max and
> cpu.max.burst:
> # echo 2000000 > /sys/fs/cgroup/test/cpu.max
> # cat /sys/fs/cgroup/test/cpu.max
> 2000000 100000
> # cat /sys/fs/cgroup/test/cpu.max.burst
> 1000
> we found that the cpu.max.burst value changed unexpectedly.
>
> In cpu_max_write(), the unit of the burst value returned
> by tg_get_cfs_burst() is microseconds, while in cpu_max_write(),
> the burst unit used for calculation should be nanoseconds,
> which leads to the bug.
>
> To fix it, we get the burst value directly from
> tg->cfs_bandwidth.burst.
>
> Reported-by: Qixin Liao <[email protected]>
> Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller")
> Signed-off-by: Cheng Yu <[email protected]>
> Signed-off-by: Zhang Qiao <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
Tested-by: Vincent Guittot <[email protected]>
> ---
> kernel/sched/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 7019a40457a6..d211d40a2edc 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -11402,7 +11402,7 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of,
> {
> struct task_group *tg = css_tg(of_css(of));
> u64 period = tg_get_cfs_period(tg);
> - u64 burst = tg_get_cfs_burst(tg);
> + u64 burst = tg->cfs_bandwidth.burst;
> u64 quota;
> int ret;
>
> --
> 2.25.1
>
>
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 49217ea147df7647cb89161b805c797487783fc0
Gitweb: https://git.kernel.org/tip/49217ea147df7647cb89161b805c797487783fc0
Author: Cheng Yu <[email protected]>
AuthorDate: Wed, 24 Apr 2024 21:24:38 +08:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Fri, 17 May 2024 09:53:54 +02:00
sched/core: Fix incorrect initialization of the 'burst' parameter in cpu_max_write()
In the cgroup v2 CPU subsystem, assuming we have a
cgroup named 'test', and we set cpu.max and cpu.max.burst:
# echo 1000000 > /sys/fs/cgroup/test/cpu.max
# echo 1000000 > /sys/fs/cgroup/test/cpu.max.burst
then we check cpu.max and cpu.max.burst:
# cat /sys/fs/cgroup/test/cpu.max
1000000 100000
# cat /sys/fs/cgroup/test/cpu.max.burst
1000000
Next we set cpu.max again and check cpu.max and
cpu.max.burst:
# echo 2000000 > /sys/fs/cgroup/test/cpu.max
# cat /sys/fs/cgroup/test/cpu.max
2000000 100000
# cat /sys/fs/cgroup/test/cpu.max.burst
1000
.. we find that the cpu.max.burst value changed unexpectedly.
In cpu_max_write(), the unit of the burst value returned
by tg_get_cfs_burst() is microseconds, while in cpu_max_write(),
the burst unit used for calculation should be nanoseconds,
which leads to the bug.
To fix it, get the burst value directly from tg->cfs_bandwidth.burst.
Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller")
Reported-by: Qixin Liao <[email protected]>
Signed-off-by: Cheng Yu <[email protected]>
Signed-off-by: Zhang Qiao <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
Tested-by: Vincent Guittot <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1a91438..f88f505 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11402,7 +11402,7 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of,
{
struct task_group *tg = css_tg(of_css(of));
u64 period = tg_get_cfs_period(tg);
- u64 burst = tg_get_cfs_burst(tg);
+ u64 burst = tg->cfs_bandwidth.burst;
u64 quota;
int ret;