cgroup/misc: Introduce misc.peak

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@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index 79a3717a5803..b92daf5d234d 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -121,6 +121,19 @@ 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;
+
+	while (true) {
+		old = atomic64_read(&res->watermark);
+		if (new_usage <= old)
+			break;
+		if (atomic64_cmpxchg(&res->watermark, old, new_usage) == old)
+			break;
+	}
+}
+
 /**
  * misc_cg_try_charge() - Try charging the misc cgroup.
  * @type: Misc res type to charge.
@@ -159,6 +172,7 @@ 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;
 
@@ -308,6 +322,29 @@ static int misc_cg_current_show(struct seq_file *sf, void *v)
 }
 
 /**
+ * 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 = atomic64_read(&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
  * @v: Arguments passed
@@ -358,6 +395,10 @@ static struct cftype misc_cg_files[] = {
 		.seq_show = misc_cg_current_show,
 	},
 	{
+		.name = "peak",
+		.seq_show = misc_cg_peak_show,
+	},
+	{
 		.name = "capacity",
 		.seq_show = misc_cg_capacity_show,
 		.flags = CFTYPE_ONLY_ON_ROOT,