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Sat, 3 Mar 2018 18:14:36 -0500 Received: from mail-by2nam01on0114.outbound.protection.outlook.com ([104.47.34.114]:65056 "EHLO NAM01-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S935002AbeCCWjG (ORCPT ); Sat, 3 Mar 2018 17:39:06 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Shaohua Li , Jens Axboe , Sasha Levin Subject: [PATCH AUTOSEL for 4.4 038/115] blk-throttle: make sure expire time isn't too big Thread-Topic: [PATCH AUTOSEL for 4.4 038/115] blk-throttle: make sure expire time isn't too big Thread-Index: AQHTsz9ULu9CD2h4SUK+4tvMXQULAA== Date: Sat, 3 Mar 2018 22:31:11 +0000 Message-ID: <20180303223010.27106-38-alexander.levin@microsoft.com> References: <20180303223010.27106-1-alexander.levin@microsoft.com> In-Reply-To: <20180303223010.27106-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB0938;7:L1Bl1d6VhpgxREhhFr9sWXgmwRkCo20W+DAO5ckNZWQOpe3FgdWDv/9iDf8/KFTEu3gjwfNBeS/iPAF5VE5lbut+v4zFjF//qG0v5Qrqd9KJXzXKQ9WjGqKCsEoM442hTAKg7w3aPEwptlefp3oCPmDmNeqO3nZwqJP0o6bftY8d4S3237MsIGmc5J6RZkrc2k7eAOLt4bIb6EqcuL4fNCjLXS09xyt4tbr7JpiBdcSHZt/4uhpFCv8Gn1v27Vez x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: af333eb7-9307-4be8-471e-08d5815791c2 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB0938; 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x-microsoft-antispam-message-info: Rzjzz0E/UFuTTnBnuVjJn4Jls7B1LVSdWBcKUwRQbEUmAo1Tw2Z5I3J5SePujhIrAA5CNOJlRkQZKJsnmIuM9HXHq4G3d1Pc0p+1zZyn7xizVXaxuL9UPfyAmLjMGJDsNRKEK9WcFGq/6qEc4FwoClpW613SQRCE0FMEY4cy+pI= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: af333eb7-9307-4be8-471e-08d5815791c2 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:31:11.1040 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0938 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Shaohua Li [ Upstream commit 06cceedcca67a93ac7f7aa93bbd9980c7496d14e ] cgroup could be throttled to a limit but when all cgroups cross high limit, queue enters a higher state and so the group should be throttled to a higher limit. It's possible the cgroup is sleeping because of throttle and other cgroups don't dispatch IO any more. In this case, nobody can trigger current downgrade/upgrade logic. To fix this issue, we could either set up a timer to wakeup the cgroup if other cgroups are idle or make sure this cgroup doesn't sleep too long. Setting up a timer means we must change the timer very frequently. This patch chooses the latter. Making cgroup sleep time not too big wouldn't change cgroup bps/iops, but could make it wakeup more frequently, which isn't a big issue because throtl_slice * 8 is already quite big. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-throttle.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 2149a1ddbacf..17bdd6b55beb 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -505,6 +505,17 @@ static void throtl_dequeue_tg(struct throtl_grp *tg) static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, unsigned long expires) { + unsigned long max_expire =3D jiffies + 8 * throtl_slice; + + /* + * Since we are adjusting the throttle limit dynamically, the sleep + * time calculated according to previous limit might be invalid. It's + * possible the cgroup sleep time is very long and no other cgroups + * have IO running so notify the limit changes. Make sure the cgroup + * doesn't sleep too long to avoid the missed notification. + */ + if (time_after(expires, max_expire)) + expires =3D max_expire; mod_timer(&sq->pending_timer, expires); throtl_log(sq, "schedule timer. delay=3D%lu jiffies=3D%lu", expires - jiffies, jiffies); --=20 2.14.1