Received-SPF: pass (google.com: domain of linux-kernel+bounces-164595-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
From: Ankur Arora <ankur.a.arora@oracle.com>
To: linux-pm@vger.kernel.org, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
        pbonzini@redhat.com, wanpengli@tencent.com, vkuznets@redhat.com,
        rafael@kernel.org, daniel.lezcano@linaro.org, peterz@infradead.org,
        arnd@arndb.de, lenb@kernel.org, mark.rutland@arm.com,
        harisokn@amazon.com, joao.m.martins@oracle.com,
        boris.ostrovsky@oracle.com, konrad.wilk@oracle.com,
        ankur.a.arora@oracle.com
Subject: [PATCH 9/9] cpuidle/poll_state: limit POLL_IDLE_RELAX_COUNT on arm64
Date: Tue, 30 Apr 2024 11:37:30 -0700
Message-Id: <20240430183730.561960-10-ankur.a.arora@oracle.com>
In-Reply-To: <20240430183730.561960-1-ankur.a.arora@oracle.com>
References: <20240430183730.561960-1-ankur.a.arora@oracle.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: 
	=?us-ascii?Q?oK5tsl+Xm7Dko1Gdgtgn/LXJBOy+/svcQdwRSIDlhtxoXwWbWdPN/8Gd1qkX?=
 =?us-ascii?Q?4luntRuqgg5CkBdyZlywWdyHcVa1FyYi2OShejm1kIE3s6/AGBKHwVARMqqe?=
 =?us-ascii?Q?hHHeq2h00VOOONzFwHQMesDqKehcl+3kWvqBT86LZiLVfd7mrTKNdhYvUa6/?=
 =?us-ascii?Q?jaQ27YOSWeeF9VHS+xwvI5jkiC+QWL3SSE8q0F/223a3xr+h7m8MiBZEed1i?=
 =?us-ascii?Q?fHh52IiUxOq/saAxwLnGNuOb1rvwBssBc7zidzVgevajiI/JqqMFDRF272gc?=
 =?us-ascii?Q?hPd6f5LLSVdAFqi89FIqYANMFFdR//uGOlXSAHPOsLZqTU8rSgMG8OXxXbnq?=
 =?us-ascii?Q?jcXkwe/qnQXYZXJI/SE7a5VC7zWw5Rpl30qI5jVrfKu9OsRzA+HDHTRXyi+A?=
 =?us-ascii?Q?QtaLI/Zj64CWa84N2SiM3eTP9Tafqr7mrXYzsDmWFqSe2DOB0m2iz7GQsQUE?=
 =?us-ascii?Q?W8XIloZ0y3M63w2kl82luY6t/BGth8sFTh+acll1U2UCZMl9XfOZn7h8uvLy?=
 =?us-ascii?Q?vsZ+SQwBE5H6I5ElzMkWxbGWV0kXLcdmFDwsaxn8XdHJxEZ8nz0UmfgXr28w?=
 =?us-ascii?Q?k7kgR1YF1laQh6tbXvARJjW+/rZeTUP8//BCrYCbFDw6c4iQqrawaqv1qZq3?=
 =?us-ascii?Q?ZwaJvHC7cA8vhZauXp7/7Ebsb0Sjfm7c6owL+Bsl/nM9/btBnOggC+nCa6XV?=
 =?us-ascii?Q?oeiReDDPAkA4m5W1VDQFccOFpiNWV5aSPSw2N2V+9RYTvSAZXroZxtHkBz9m?=
 =?us-ascii?Q?dSs+kC+29PWDt6XWX/PXLHDurXqtMRU7E7McyrphMz6aNriGdF1cGuitjAIf?=
 =?us-ascii?Q?QoA3WdQ0O+XZMCPWjyNRiYFTQTsMTNymtxbH+ZazX+R/5n1kTqd0ryr5GwsS?=
 =?us-ascii?Q?swZkbcgx6TAJob5OffjW0uoCXqCMAI90MpokDFWrTKfHBgMkWBmjyT3jgfyC?=
 =?us-ascii?Q?fAdj9JxRYHBD76iJ3PHtTCLL7tZO6CLytfKLXlR1xgq9Fv7AvKGRnmI1yKiT?=
 =?us-ascii?Q?Et4IVw8RDYv80/k+WDvdzNo7o4FzkaNKzt+egtfrvxwUF1xsrsiuSzF5Ru8B?=
 =?us-ascii?Q?nP/L9wkrXhMNAPcYNsrsp3bpQQpY1TKtMmDm4Uoc2xnMYtJcVU4IJ+LknQN0?=
 =?us-ascii?Q?4AKeW2GALOiqm8IjpouOzjaih2He18zlrqmj3TqpSsiYP3eH1KC7/02G861t?=
 =?us-ascii?Q?6Ljcmvay5DUYy2zcIfU8VcNx2YMD4j1GEseo2JiETo4SgmYB1aXKFbfA7wpq?=
 =?us-ascii?Q?2MUuOeZ2cKalo4983G6A9odcqCKaSozD7H4yA2uQ3yvLcVodRMzqf8l+nQsW?=
 =?us-ascii?Q?efkfNs8yrVvEWdqDJPzvaVVxFDEokpYCdAj4p/rOCV8ctMOG+yo3kCq99Dj/?=
 =?us-ascii?Q?G9+34AyfTGjZA0cbXY7wyMXHeNwoir5eLG6BJfnair+RJ00pCaoUyOr87ld1?=
 =?us-ascii?Q?cQkhqvi4BAD3Hj5liI5J4RwpvhEqr0xYeCDDiVCRSNJc8clqzKfIXmmdosb7?=
 =?us-ascii?Q?TNIlLyS8ibu5Lzkylhy7C0I+6nJBD9j8hlCG8awCu8nBZ6r/wjnWjl4usSaO?=
 =?us-ascii?Q?RnV0DK5Oibb5GpqEkgyK2WtpIL91CRxy6p0O2nkpfgl7zBjKVCn0V+hnEo11?=
 =?us-ascii?Q?cg=3D=3D?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 
	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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 449f83a1-f209-461e-0164-08dc6944a845
X-MS-Exchange-CrossTenant-AuthSource: CO6PR10MB5409.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Apr 2024 18:37:58.2531
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: O/Uhd4eUf601epdBp+Ib6lzn008ube9W9oAV7pz1Zm0DPryvbeFJcThWxYxTeVoOGw3Sq2DejQ5lbU0h78a1Fg/PcjR6XoOyvW0su/2ZGlw=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR10MB6308
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.293,Aquarius:18.0.1011,Hydra:6.0.650,FMLib:17.11.176.26
 definitions=2024-04-30_11,2024-04-30_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 bulkscore=0 adultscore=0
 phishscore=0 mlxscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2404010000
 definitions=main-2404300134
X-Proofpoint-ORIG-GUID: V1oLAXowiiGx7BQXRAD6b1HlqZHfZhjI
X-Proofpoint-GUID: V1oLAXowiiGx7BQXRAD6b1HlqZHfZhjI

smp_cond_load_relaxed(), in its generic polling variant polls on the
loop condition, waiting for it to change, eventually exiting the loop
if the time limit has been exceeded.

To limit the frequency of the time check it is done only once every
POLL_IDLE_RELAX_COUNT iterations.

arm64, however uses an event based mechanism, where instead of polling,
we wait for store to a region.

Limit the POLL_IDLE_RELAX_COUNT to 1 for that case.

Suggested-by: Haris Okanovic <harisokn@amazon.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 drivers/cpuidle/poll_state.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c
index 532e4ed19e0f..b69fe7b67cb4 100644
--- a/drivers/cpuidle/poll_state.c
+++ b/drivers/cpuidle/poll_state.c
@@ -8,7 +8,18 @@
 #include <linux/sched/clock.h>
 #include <linux/sched/idle.h>
 
+#ifdef CONFIG_ARM64
+/*
+ * POLL_IDLE_RELAX_COUNT determines how often we check for timeout
+ * while polling for TIF_NEED_RESCHED in thread_info->flags.
+ *
+ * Set this to a low value since arm64, instead of polling, uses a
+ * event based mechanism.
+ */
+#define POLL_IDLE_RELAX_COUNT	1
+#else
 #define POLL_IDLE_RELAX_COUNT	200
+#endif
 
 static int __cpuidle poll_idle(struct cpuidle_device *dev,
 			       struct cpuidle_driver *drv, int index)
-- 
2.39.3