linux-kernel - [tip: timers/core] x86/vdso: Mark the TSC clocksource path likely

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Date:   Mon, 17 Feb 2020 15:12:00 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: timers/core] x86/vdso: Mark the TSC clocksource path likely

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     50e818715821b89c7abac90a97721f106e893d83
Gitweb:        https://git.kernel.org/tip/50e818715821b89c7abac90a97721f106e893d83
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Fri, 07 Feb 2020 13:38:48 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Mon, 17 Feb 2020 14:40:19 +01:00

x86/vdso: Mark the TSC clocksource path likely

Jumping out of line for the TSC clcoksource read is creating awful
code. TSC is likely to be the clocksource at least on bare metal and the PV
interfaces are sufficiently more work that the jump over the TSC read is
just in the noise.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@....com>
Link: https://lkml.kernel.org/r/20200207124402.328922847@linutronix.de

---
 arch/x86/include/asm/vdso/gettimeofday.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
index 6ee1f7d..264d4fd 100644
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -243,7 +243,7 @@ static u64 vread_hvclock(void)
 
 static inline u64 __arch_get_hw_counter(s32 clock_mode)
 {
-	if (clock_mode == VCLOCK_TSC)
+	if (likely(clock_mode == VCLOCK_TSC))
 		return (u64)rdtsc_ordered();
 	/*
 	 * For any memory-mapped vclock type, we need to make sure that gcc