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From: Jisheng Zhang <jszhang@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Schaffner Tobias <tobias.schaffner@siemens.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org
Subject: [PATCH RT 1/3] asm-generic/preempt: also check preempt_lazy_count for should_resched() etc.
Date: Thu, 11 May 2023 00:24:04 +0800	[thread overview]
Message-ID: <20230510162406.1955-2-jszhang@kernel.org> (raw)
In-Reply-To: <20230510162406.1955-1-jszhang@kernel.org>

lazy preempt count is great mechanism to help ordinary SCHED_OTHER
tasks' throughput Under PREEMPT_RT. But current implementation relies
on each arch-specific code to check the preempt_lazy_count in
should_resched() and __preempt_count_dec_and_test(), if the arch, e.g
riscv use the asm-generic preempt implementation, it losts the great
lazy preempt mechanism.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 include/asm-generic/preempt.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index b4d43a4af5f7..b583e7c38ccf 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -59,6 +59,11 @@ static __always_inline void __preempt_count_sub(int val)
 	*preempt_count_ptr() -= val;
 }
 
+#ifdef CONFIG_PREEMPT_LAZY
+#define preempt_lazy_count()		(current_thread_info()->preempt_lazy_count)
+#else
+#define preempt_lazy_count()		(0)
+#endif
 static __always_inline bool __preempt_count_dec_and_test(void)
 {
 	/*
@@ -66,7 +71,7 @@ static __always_inline bool __preempt_count_dec_and_test(void)
 	 * operations; we cannot use PREEMPT_NEED_RESCHED because it might get
 	 * lost.
 	 */
-	return !--*preempt_count_ptr() && tif_need_resched();
+	return !--*preempt_count_ptr() && !preempt_lazy_count() && tif_need_resched();
 }
 
 /*
@@ -75,6 +80,7 @@ static __always_inline bool __preempt_count_dec_and_test(void)
 static __always_inline bool should_resched(int preempt_offset)
 {
 	return unlikely(preempt_count() == preempt_offset &&
+			!preempt_lazy_count() &&
 			tif_need_resched());
 }
 
-- 
2.40.1


WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Schaffner Tobias <tobias.schaffner@siemens.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org
Subject: [PATCH RT 1/3] asm-generic/preempt: also check preempt_lazy_count for should_resched() etc.
Date: Thu, 11 May 2023 00:24:04 +0800	[thread overview]
Message-ID: <20230510162406.1955-2-jszhang@kernel.org> (raw)
In-Reply-To: <20230510162406.1955-1-jszhang@kernel.org>

lazy preempt count is great mechanism to help ordinary SCHED_OTHER
tasks' throughput Under PREEMPT_RT. But current implementation relies
on each arch-specific code to check the preempt_lazy_count in
should_resched() and __preempt_count_dec_and_test(), if the arch, e.g
riscv use the asm-generic preempt implementation, it losts the great
lazy preempt mechanism.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 include/asm-generic/preempt.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index b4d43a4af5f7..b583e7c38ccf 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -59,6 +59,11 @@ static __always_inline void __preempt_count_sub(int val)
 	*preempt_count_ptr() -= val;
 }
 
+#ifdef CONFIG_PREEMPT_LAZY
+#define preempt_lazy_count()		(current_thread_info()->preempt_lazy_count)
+#else
+#define preempt_lazy_count()		(0)
+#endif
 static __always_inline bool __preempt_count_dec_and_test(void)
 {
 	/*
@@ -66,7 +71,7 @@ static __always_inline bool __preempt_count_dec_and_test(void)
 	 * operations; we cannot use PREEMPT_NEED_RESCHED because it might get
 	 * lost.
 	 */
-	return !--*preempt_count_ptr() && tif_need_resched();
+	return !--*preempt_count_ptr() && !preempt_lazy_count() && tif_need_resched();
 }
 
 /*
@@ -75,6 +80,7 @@ static __always_inline bool __preempt_count_dec_and_test(void)
 static __always_inline bool should_resched(int preempt_offset)
 {
 	return unlikely(preempt_count() == preempt_offset &&
+			!preempt_lazy_count() &&
 			tif_need_resched());
 }
 
-- 
2.40.1


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  reply	other threads:[~2023-05-10 16:35 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-10 16:24 [PATCH RT 0/3] riscv: add PREEMPT_RT support Jisheng Zhang
2023-05-10 16:24 ` Jisheng Zhang
2023-05-10 16:24 ` Jisheng Zhang [this message]
2023-05-10 16:24   ` [PATCH RT 1/3] asm-generic/preempt: also check preempt_lazy_count for should_resched() etc Jisheng Zhang
2023-05-10 16:24 ` [PATCH RT 2/3] riscv: add lazy preempt support Jisheng Zhang
2023-05-10 16:24   ` Jisheng Zhang
2023-05-10 16:24 ` [PATCH RT 3/3] riscv: Allow to enable RT Jisheng Zhang
2023-05-10 16:24   ` Jisheng Zhang
2023-10-23 16:33 ` [PATCH RT 0/3] riscv: add PREEMPT_RT support Schaffner, Tobias
2023-10-23 16:33   ` Schaffner, Tobias
2023-10-23 16:40   ` Jisheng Zhang
2023-10-23 16:40     ` Jisheng Zhang
2023-10-24  6:18     ` Sebastian Andrzej Siewior
2023-10-24  6:18       ` Sebastian Andrzej Siewior
2023-10-31 14:43       ` Jisheng Zhang
2023-10-31 14:43         ` Jisheng Zhang
2023-10-31 15:34         ` Sebastian Andrzej Siewior
2023-10-31 15:34           ` Sebastian Andrzej Siewior

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