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From:   Chen Wandun <chenwandun@huawei.com>
To:     <linux-kernel@vger.kernel.org>, <hannes@cmpxchg.org>,
        <surenb@google.com>, <alexs@kernel.org>, <corbet@lwn.net>,
        <linux-doc@vger.kernel.org>
Subject: [PATCH 1/2] psi: add support for multi level pressure stall trigger
Date:   Mon, 16 May 2022 11:35:23 +0800
Message-ID: <20220516033524.3130816-1-chenwandun@huawei.com>
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Precedence: bulk

Nowadays, psi events are triggered when stall time exceed
stall threshold, but no any different between these events.

Actually, events can be divide into multi level, each level
represent a different stall pressure, that is help to identify
pressure information more accurately.

echo "some 150000 350000 1000000" > /proc/pressure/memory would
add [150ms, 350ms) threshold for partial memory stall measured
within 1sec time window.

Signed-off-by: Chen Wandun <chenwandun@huawei.com>
---
 include/linux/psi_types.h |  3 ++-
 kernel/sched/psi.c        | 19 +++++++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index c7fe7c089718..2b1393c8bf90 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -119,7 +119,8 @@ struct psi_trigger {
 	enum psi_states state;
 
 	/* User-spacified threshold in ns */
-	u64 threshold;
+	u64 min_threshold;
+	u64 max_threshold;
 
 	/* List node inside triggers list */
 	struct list_head node;
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 6f9533c95b0a..17dd233b533a 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -541,7 +541,7 @@ static u64 update_triggers(struct psi_group *group, u64 now)
 
 			/* Calculate growth since last update */
 			growth = window_update(&t->win, now, total[t->state]);
-			if (growth < t->threshold)
+			if (growth < t->min_threshold || growth >= t->max_threshold)
 				continue;
 
 			t->pending_event = true;
@@ -1087,15 +1087,18 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
 {
 	struct psi_trigger *t;
 	enum psi_states state;
-	u32 threshold_us;
+	u32 min_threshold_us;
+	u32 max_threshold_us;
 	u32 window_us;
 
 	if (static_branch_likely(&psi_disabled))
 		return ERR_PTR(-EOPNOTSUPP);
 
-	if (sscanf(buf, "some %u %u", &threshold_us, &window_us) == 2)
+	if (sscanf(buf, "some %u %u %u", &min_threshold_us,
+				&max_threshold_us, &window_us) == 3)
 		state = PSI_IO_SOME + res * 2;
-	else if (sscanf(buf, "full %u %u", &threshold_us, &window_us) == 2)
+	else if (sscanf(buf, "full %u %u %u", &min_threshold_us,
+				&max_threshold_us, &window_us) == 3)
 		state = PSI_IO_FULL + res * 2;
 	else
 		return ERR_PTR(-EINVAL);
@@ -1107,8 +1110,11 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
 		window_us > WINDOW_MAX_US)
 		return ERR_PTR(-EINVAL);
 
+	if (min_threshold_us >= max_threshold_us)
+		return ERR_PTR(-EINVAL);
+
 	/* Check threshold */
-	if (threshold_us == 0 || threshold_us > window_us)
+	if (max_threshold_us > window_us)
 		return ERR_PTR(-EINVAL);
 
 	t = kmalloc(sizeof(*t), GFP_KERNEL);
@@ -1117,7 +1123,8 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
 
 	t->group = group;
 	t->state = state;
-	t->threshold = threshold_us * NSEC_PER_USEC;
+	t->min_threshold = min_threshold_us * NSEC_PER_USEC;
+	t->max_threshold = max_threshold_us * NSEC_PER_USEC;
 	t->win.size = window_us * NSEC_PER_USEC;
 	window_reset(&t->win, 0, 0, 0);
 
-- 
2.25.1