linux-kernel - [PATCH V2 1/4] LoongArch: Reduce min_delta for the arch clockevent device

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Message-ID: <20241117054017.3938700-1-chenhuacai@loongson.cn>
Date: Sun, 17 Nov 2024 13:40:14 +0800
From: Huacai Chen <chenhuacai@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: loongarch@...ts.linux.dev,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-rt-devel@...ts.linux.dev,
	Xuerui Wang <kernel@...0n.name>,
	Jiaxun Yang <jiaxun.yang@...goat.com>,
	linux-kernel@...r.kernel.org,
	loongson-kernel@...ts.loongnix.cn,
	Huacai Chen <chenhuacai@...ngson.cn>
Subject: [PATCH V2 1/4] LoongArch: Reduce min_delta for the arch clockevent device

Now the min_delta is 0x600 (1536) for LoongArch's constant clockevent
device. For a 100MHz hardware timer this means ~15us. This is a little
big, especially for PREEMPT_RT enabled kernels. So reduce it to 100 for
PREEMPT_RT kernel, and 1000 for others (we don't want too small values
to affect performance).

Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
 arch/loongarch/kernel/time.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/kernel/time.c b/arch/loongarch/kernel/time.c
index 46d7d40c87e3..a07d7eff4dc5 100644
--- a/arch/loongarch/kernel/time.c
+++ b/arch/loongarch/kernel/time.c
@@ -127,7 +127,11 @@ void sync_counter(void)
 int constant_clockevent_init(void)
 {
 	unsigned int cpu = smp_processor_id();
-	unsigned long min_delta = 0x600;
+#ifdef CONFIG_PREEMPT_RT
+	unsigned long min_delta = 100;
+#else
+	unsigned long min_delta = 1000;
+#endif
 	unsigned long max_delta = (1UL << 48) - 1;
 	struct clock_event_device *cd;
 	static int irq = 0, timer_irq_installed = 0;
-- 
2.43.5