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From: Mihai Carabas <mihai.carabas@oracle.com>
To: linux-arm-kernel@lists.infradead.org
Cc: kvm@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, 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, akpm@linux-foundation.org,
	pmladek@suse.com, peterz@infradead.org, dianders@chromium.org,
	npiggin@gmail.com, rick.p.edgecombe@intel.com,
	joao.m.martins@oracle.com, juerg.haefliger@canonical.com,
	mic@digikod.net, mihai.carabas@oracle.com, arnd@arndb.de,
	ankur.a.arora@oracle.com
Subject: [PATCH 7/7] cpuidle/poll_state: replace cpu_relax with smp_cond_load_relaxed
Date: Mon, 20 Nov 2023 16:01:38 +0200	[thread overview]
Message-ID: <1700488898-12431-8-git-send-email-mihai.carabas@oracle.com> (raw)
In-Reply-To: <1700488898-12431-1-git-send-email-mihai.carabas@oracle.com>

cpu_relax on ARM64 does a simple "yield". Thus we replace it with
smp_cond_load_relaxed which basically does a "wfe".

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
---
 drivers/cpuidle/poll_state.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c
index 9b6d90a72601..440cd713e39a 100644
--- a/drivers/cpuidle/poll_state.c
+++ b/drivers/cpuidle/poll_state.c
@@ -26,12 +26,16 @@ static int __cpuidle poll_idle(struct cpuidle_device *dev,
 
 		limit = cpuidle_poll_time(drv, dev);
 
-		while (!need_resched()) {
-			cpu_relax();
-			if (loop_count++ < POLL_IDLE_RELAX_COUNT)
-				continue;
-
+		for (;;) {
 			loop_count = 0;
+
+			smp_cond_load_relaxed(&current_thread_info()->flags,
+					      (VAL & _TIF_NEED_RESCHED) ||
+					      (loop_count++ >= POLL_IDLE_RELAX_COUNT));
+
+			if (loop_count < POLL_IDLE_RELAX_COUNT)
+				break;
+
 			if (local_clock_noinstr() - time_start > limit) {
 				dev->poll_time_limit = true;
 				break;
-- 
1.8.3.1


WARNING: multiple messages have this Message-ID (diff)
From: Mihai Carabas <mihai.carabas@oracle.com>
To: linux-arm-kernel@lists.infradead.org
Cc: kvm@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, 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, akpm@linux-foundation.org,
	pmladek@suse.com, peterz@infradead.org, dianders@chromium.org,
	npiggin@gmail.com, rick.p.edgecombe@intel.com,
	joao.m.martins@oracle.com, juerg.haefliger@canonical.com,
	mic@digikod.net, mihai.carabas@oracle.com, arnd@arndb.de,
	ankur.a.arora@oracle.com
Subject: [PATCH 7/7] cpuidle/poll_state: replace cpu_relax with smp_cond_load_relaxed
Date: Mon, 20 Nov 2023 16:01:38 +0200	[thread overview]
Message-ID: <1700488898-12431-8-git-send-email-mihai.carabas@oracle.com> (raw)
In-Reply-To: <1700488898-12431-1-git-send-email-mihai.carabas@oracle.com>

cpu_relax on ARM64 does a simple "yield". Thus we replace it with
smp_cond_load_relaxed which basically does a "wfe".

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
---
 drivers/cpuidle/poll_state.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c
index 9b6d90a72601..440cd713e39a 100644
--- a/drivers/cpuidle/poll_state.c
+++ b/drivers/cpuidle/poll_state.c
@@ -26,12 +26,16 @@ static int __cpuidle poll_idle(struct cpuidle_device *dev,
 
 		limit = cpuidle_poll_time(drv, dev);
 
-		while (!need_resched()) {
-			cpu_relax();
-			if (loop_count++ < POLL_IDLE_RELAX_COUNT)
-				continue;
-
+		for (;;) {
 			loop_count = 0;
+
+			smp_cond_load_relaxed(&current_thread_info()->flags,
+					      (VAL & _TIF_NEED_RESCHED) ||
+					      (loop_count++ >= POLL_IDLE_RELAX_COUNT));
+
+			if (loop_count < POLL_IDLE_RELAX_COUNT)
+				break;
+
 			if (local_clock_noinstr() - time_start > limit) {
 				dev->poll_time_limit = true;
 				break;
-- 
1.8.3.1


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  parent reply	other threads:[~2023-11-20 15:16 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-20 14:01 [PATCH v2] Enable haltpoll for arm64 Mihai Carabas
2023-11-20 14:01 ` Mihai Carabas
2023-11-20 14:01 ` [PATCH 1/7] x86: Move ARCH_HAS_CPU_RELAX to arch Mihai Carabas
2023-11-20 14:01   ` Mihai Carabas
2023-11-27 14:44   ` Petr Mladek
2023-11-27 14:44     ` Petr Mladek
2023-11-28 14:09     ` Mihai Carabas
2023-11-28 14:09       ` Mihai Carabas
2023-11-20 14:01 ` [PATCH 2/7] x86/kvm: Move haltpoll_want() to be arch defined Mihai Carabas
2023-11-20 14:01   ` Mihai Carabas
2023-11-29 20:55   ` Rafael J. Wysocki
2023-11-29 20:55     ` Rafael J. Wysocki
2023-11-20 14:01 ` [PATCH 3/7] governors/haltpoll: Drop kvm_para_available() check Mihai Carabas
2023-11-20 14:01   ` Mihai Carabas
2023-11-20 14:01 ` [PATCH 4/7] arm64: Select ARCH_HAS_CPU_RELAX Mihai Carabas
2023-11-20 14:01   ` Mihai Carabas
2023-11-20 14:01 ` [PATCH 5/7] arm64: Define TIF_POLLING_NRFLAG Mihai Carabas
2023-11-20 14:01   ` Mihai Carabas
2023-11-20 14:01 ` [PATCH 6/7] cpuidle-haltpoll: ARM64 support Mihai Carabas
2023-11-20 14:01   ` Mihai Carabas
2023-11-20 14:01 ` Mihai Carabas [this message]
2023-11-20 14:01   ` [PATCH 7/7] cpuidle/poll_state: replace cpu_relax with smp_cond_load_relaxed Mihai Carabas
2023-11-22 20:51   ` Christoph Lameter
2023-11-22 20:51     ` Christoph Lameter
2023-11-22 21:33     ` Mihai Carabas
2023-11-22 21:33       ` Mihai Carabas
2023-11-27 20:17       ` Christoph Lameter (Ampere)
2023-11-27 20:17         ` Christoph Lameter (Ampere)
2023-12-01  6:59         ` Ankur Arora
2023-12-01  6:59           ` Ankur Arora
2023-12-11 11:46   ` Will Deacon
2023-12-11 11:46     ` Will Deacon
2024-01-28 21:22     ` Mihai Carabas
2024-01-28 21:22       ` Mihai Carabas
2024-01-29 18:15       ` Will Deacon
2024-01-29 18:15         ` Will Deacon
2024-02-05 12:28         ` Mihai Carabas
2024-02-05 12:28           ` Mihai Carabas
2024-02-05 19:33           ` Ankur Arora
2024-02-05 19:33             ` Ankur Arora
2024-01-17 21:19 ` [PATCH v2] Enable haltpoll for arm64 Christoph Lameter (Ampere)
2024-01-17 21:19   ` Christoph Lameter (Ampere)
2024-01-25 14:39 ` Mihai Carabas
2024-01-25 14:39   ` Mihai Carabas
2024-01-25 15:16   ` Rafael J. Wysocki
2024-01-25 15:16     ` Rafael J. Wysocki

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