linux-kernel - [tip: timers/vdso] vdso: Move arch related data before basetime

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Message-ID: <174099857821.10177.8446012809637932009.tip-bot2@tip-bot2>
Date: Mon, 03 Mar 2025 10:42:58 -0000
From: "tip-bot2 for Anna-Maria Behnsen" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Anna-Maria Behnsen" <anna-maria@...utronix.de>,
 Nam Cao <namcao@...utronix.de>, thomas.weissschuh@...utronix.de,
 Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: timers/vdso] vdso: Move arch related data before basetime

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

Commit-ID:     ece1e22d2caea94d1d836c22c4262c221f3b7f95
Gitweb:        https://git.kernel.org/tip/ece1e22d2caea94d1d836c22c4262c221f3b7f95
Author:        Anna-Maria Behnsen <anna-maria@...utronix.de>
AuthorDate:    Tue, 25 Feb 2025 13:36:50 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Mon, 03 Mar 2025 10:24:35 +01:00

vdso: Move arch related data before basetime

Architecture related vdso data is required in the fastpath when acquiring
CLOCK_MONOTONIC or CLOCK_REALTIME. At the moment, this information is
located at the end of the vdso_time_data structure. The whole structure has
to be loaded into the cache to be able to access this information.

To minimize the number of required cachelines, move the architecture
specific vdso data struct right before the basetime (basetime information
is required anyway).

This change does not have an impact on architectures with
CONFIG_ARCH_HAS_VDSO_DATA=n. All other architectures could spare reading
unnecessary cachelines.

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Signed-off-by: Nam Cao <namcao@...utronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 include/vdso/datapage.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 1df22e8..bcd19c2 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -70,6 +70,8 @@ struct vdso_timestamp {
 
 /**
  * struct vdso_time_data - vdso datapage representation
+ * @arch_data:		architecture specific data (optional, defaults
+ *			to an empty struct)
  * @seq:		timebase sequence counter
  * @clock_mode:		clock mode
  * @cycle_last:		timebase at clocksource init
@@ -83,8 +85,6 @@ struct vdso_timestamp {
  * @tz_dsttime:		type of DST correction
  * @hrtimer_res:	hrtimer resolution
  * @__unused:		unused
- * @arch_data:		architecture specific data (optional, defaults
- *			to an empty struct)
  *
  * vdso_time_data will be accessed by 64 bit and compat code at the same time
  * so we should be careful before modifying this structure.
@@ -105,6 +105,8 @@ struct vdso_timestamp {
  * offset must be zero.
  */
 struct vdso_time_data {
+	struct arch_vdso_time_data arch_data;
+
 	u32			seq;
 
 	s32			clock_mode;
@@ -125,8 +127,6 @@ struct vdso_time_data {
 	s32			tz_dsttime;
 	u32			hrtimer_res;
 	u32			__unused;
-
-	struct arch_vdso_time_data arch_data;
 } ____cacheline_aligned;
 
 #define vdso_clock vdso_time_data