linux-kernel - [PATCH] blk-cgroup: turn on psi memstall stuff

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Message-ID: <20190709214129.GK657710@devbig004.ftw2.facebook.com>
Date:   Tue, 9 Jul 2019 14:41:29 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, Josef Bacik <josef@...icpanda.com>
Subject: [PATCH] blk-cgroup: turn on psi memstall stuff

From: Josef Bacik <jbacik@...com>

With the psi stuff in place we can use the memstall flag to indicate
pressure that happens from throttling.

Signed-off-by: Josef Bacik <jbacik@...com>
Signed-off-by: Tejun Heo <tj@...nel.org>
---
 block/blk-cgroup.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1f7127b03490..6ed515b78cb3 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -29,6 +29,7 @@
 #include <linux/ctype.h>
 #include <linux/blk-cgroup.h>
 #include <linux/tracehook.h>
+#include <linux/psi.h>
 #include "blk.h"
 
 #define MAX_KEY_LEN 100
@@ -1644,6 +1645,7 @@ static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now)
  */
 static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
 {
+	unsigned long pflags;
 	u64 now = ktime_to_ns(ktime_get());
 	u64 exp;
 	u64 delay_nsec = 0;
@@ -1670,11 +1672,8 @@ static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
 	 */
 	delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC);
 
-	/*
-	 * TODO: the use_memdelay flag is going to be for the upcoming psi stuff
-	 * that hasn't landed upstream yet.  Once that stuff is in place we need
-	 * to do a psi_memstall_enter/leave if memdelay is set.
-	 */
+	if (use_memdelay)
+		psi_memstall_enter(&pflags);
 
 	exp = ktime_add_ns(now, delay_nsec);
 	tok = io_schedule_prepare();
@@ -1684,6 +1683,9 @@ static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
 			break;
 	} while (!fatal_signal_pending(current));
 	io_schedule_finish(tok);
+
+	if (use_memdelay)
+		psi_memstall_leave(&pflags);
 }
 
 /**