The following commit has been merged into the sched/hrtick branch of tip:
Commit-ID: b27801189f7fc97a960a96a63b78dcabbb67a52f
Gitweb: https://git.kernel.org/tip/b27801189f7fc97a960a96a63b78dcabbb67a52f
Author: Thomas Gleixner <tglx@kernel.org>
AuthorDate: Tue, 24 Feb 2026 17:36:24 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 27 Feb 2026 16:40:07 +01:00
x86: Inline TSC reads in timekeeping
Avoid the overhead of the indirect call for a single instruction to read
the TSC.
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260224163429.741886362@kernel.org
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/clock_inlined.h | 14 ++++++++++++++
arch/x86/kernel/tsc.c | 1 +
3 files changed, 16 insertions(+)
create mode 100644 arch/x86/include/asm/clock_inlined.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e2df1b1..d337d8d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -141,6 +141,7 @@ config X86
select ARCH_USE_SYM_ANNOTATIONS
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
+ select ARCH_WANTS_CLOCKSOURCE_READ_INLINE if X86_64
select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select ARCH_WANTS_NO_INSTR
select ARCH_WANT_GENERAL_HUGETLB
diff --git a/arch/x86/include/asm/clock_inlined.h b/arch/x86/include/asm/clock_inlined.h
new file mode 100644
index 0000000..29902c5
--- /dev/null
+++ b/arch/x86/include/asm/clock_inlined.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_CLOCK_INLINED_H
+#define _ASM_X86_CLOCK_INLINED_H
+
+#include <asm/tsc.h>
+
+struct clocksource;
+
+static __always_inline u64 arch_inlined_clocksource_read(struct clocksource *cs)
+{
+ return (u64)rdtsc_ordered();
+}
+
+#endif
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index d9aa694..74a26fb 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1201,6 +1201,7 @@ static struct clocksource clocksource_tsc = {
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS |
CLOCK_SOURCE_VALID_FOR_HRES |
+ CLOCK_SOURCE_CAN_INLINE_READ |
CLOCK_SOURCE_MUST_VERIFY |
CLOCK_SOURCE_VERIFY_PERCPU,
.id = CSID_X86_TSC,