Re: [PATCH] kfence: unconditionally use unbound work queue

[Alexander Potapenko]

On Fri, May 21, 2021 at 1:16 PM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> Unconditionally use unbound work queue, and not just if
> wq_power_efficient is true. Because if the system is idle, KFENCE may
> wait, and by being run on the unbound work queue, we permit the
> scheduler to make better scheduling decisions and not require pinning
> KFENCE to the same CPU upon waking up.
>
> Fixes: 36f0b35d0894 ("kfence: use power-efficient work queue to run delayed work")
> Reported-by: Hillf Danton <hdanton@xxxxxxxx>
> Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>

> ---
>  mm/kfence/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 4d21ac44d5d3..d7666ace9d2e 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -636,7 +636,7 @@ static void toggle_allocation_gate(struct work_struct *work)
>         /* Disable static key and reset timer. */
>         static_branch_disable(&kfence_allocation_key);
>  #endif
> -       queue_delayed_work(system_power_efficient_wq, &kfence_timer,
> +       queue_delayed_work(system_unbound_wq, &kfence_timer,
>                            msecs_to_jiffies(kfence_sample_interval));
>  }
>  static DECLARE_DELAYED_WORK(kfence_timer, toggle_allocation_gate);
> @@ -666,7 +666,7 @@ void __init kfence_init(void)
>         }
>
>         WRITE_ONCE(kfence_enabled, true);
> -       queue_delayed_work(system_power_efficient_wq, &kfence_timer, 0);
> +       queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
>         pr_info("initialized - using %lu bytes for %d objects at 0x%p-0x%p\n", KFENCE_POOL_SIZE,
>                 CONFIG_KFENCE_NUM_OBJECTS, (void *)__kfence_pool,
>                 (void *)(__kfence_pool + KFENCE_POOL_SIZE));
> --
> 2.31.1.818.g46aad6cb9e-goog
>


-- 
Alexander Potapenko
Software Engineer

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