On 2024/7/2 8:41, Xiu Jianfeng wrote:
> Introduce misc.peak to record the historical maximum usage of the
> resource, as in some scenarios the value of misc.max could be
> adjusted based on the peak usage of the resource.
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx>
>
> ---
> v2: use cmpxchg to update the watermark
> ---
> Documentation/admin-guide/cgroup-v2.rst | 9 ++++++
> include/linux/misc_cgroup.h | 2 ++
> kernel/cgroup/misc.c | 39 +++++++++++++++++++++++++
> 3 files changed, 50 insertions(+)
>
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index ae0fdb6fc618..468a95379009 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -2646,6 +2646,15 @@ Miscellaneous controller provides 3 interface files. If two misc resources (res_
> res_a 3
> res_b 0
>
> + misc.peak
> + A read-only flat-keyed file shown in all cgroups. It shows the
> + historical maximum usage of the resources in the cgroup and its
> + children.::
> +
> + $ cat misc.peak
> + res_a 10
> + res_b 8
> +
> misc.max
> A read-write flat-keyed file shown in the non root cgroups. Allowed
> maximum usage of the resources in the cgroup and its children.::
> diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
> index e799b1f8d05b..faf72a537596 100644
> --- a/include/linux/misc_cgroup.h
> +++ b/include/linux/misc_cgroup.h
> @@ -30,11 +30,13 @@ struct misc_cg;
> /**
> * struct misc_res: Per cgroup per misc type resource
> * @max: Maximum limit on the resource.
> + * @watermark: Historical maximum usage of the resource.
> * @usage: Current usage of the resource.
> * @events: Number of times, the resource limit exceeded.
> */
> struct misc_res {
> u64 max;
> + u64 watermark;
> atomic64_t usage;
> atomic64_t events;
> };
> diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
> index 79a3717a5803..42642a96f4dc 100644
> --- a/kernel/cgroup/misc.c
> +++ b/kernel/cgroup/misc.c
> @@ -121,6 +121,17 @@ static void misc_cg_cancel_charge(enum misc_res_type type, struct misc_cg *cg,
> misc_res_name[type]);
> }
>
> +static void misc_cg_update_watermark(struct misc_res *res, u64 new_usage)
> +{
> + u64 old;
> +
> + do {
> + old = READ_ONCE(res->watermark);
> + if (cmpxchg(&res->watermark, old, new_usage) == old)
> + break;
> + } while (0);
oops! should be while (1) here.
> +}
> +
> /**
> * misc_cg_try_charge() - Try charging the misc cgroup.
> * @type: Misc res type to charge.
> @@ -159,6 +170,7 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
> ret = -EBUSY;
> goto err_charge;
> }
> + misc_cg_update_watermark(res, new_usage);
> }
> return 0;
>
> @@ -307,6 +319,29 @@ static int misc_cg_current_show(struct seq_file *sf, void *v)
> return 0;
> }
>
> +/**
> + * misc_cg_peak_show() - Show the peak usage of the misc cgroup.
> + * @sf: Interface file
> + * @v: Arguments passed
> + *
> + * Context: Any context.
> + * Return: 0 to denote successful print.
> + */
> +static int misc_cg_peak_show(struct seq_file *sf, void *v)
> +{
> + int i;
> + u64 watermark;
> + struct misc_cg *cg = css_misc(seq_css(sf));
> +
> + for (i = 0; i < MISC_CG_RES_TYPES; i++) {
> + watermark = READ_ONCE(cg->res[i].watermark);
> + if (READ_ONCE(misc_res_capacity[i]) || watermark)
> + seq_printf(sf, "%s %llu\n", misc_res_name[i], watermark);
> + }
> +
> + return 0;
> +}
> +
> /**
> * misc_cg_capacity_show() - Show the total capacity of misc res on the host.
> * @sf: Interface file
> @@ -357,6 +392,10 @@ static struct cftype misc_cg_files[] = {
> .name = "current",
> .seq_show = misc_cg_current_show,
> },
> + {
> + .name = "peak",
> + .seq_show = misc_cg_peak_show,
> + },
> {
> .name = "capacity",
> .seq_show = misc_cg_capacity_show,
