linux-kernel - [PATCH v3 2/2] x86/vdso: implement clock_gettime(CLOCK_MONOTONIC

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Date:   Wed, 5 Jun 2019 14:41:45 +0000
From:   "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>
To:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Vas Dias <jason.vas.dias@...il.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v3 2/2] x86/vdso: implement clock_gettime(CLOCK_MONOTONIC_RAW,
 ...)

From: Alexander Sverdlin <alexander.sverdlin@...ia.com>

Add CLOCK_MONOTONIC_RAW to the existing clock_gettime() vDSO
implementation. This is based on the ideas of Jason Vas Dias and comments
of Thomas Gleixner.

Test program from the previous patch shows the following improvement:

Clock                   Before  After   Diff
-----                   ------  -----   ----
CLOCK_MONOTONIC_RAW     44.9M   359.6M  +700%

Link: https://lore.kernel.org/patchwork/patch/933583/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=198961
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Jason Vas Dias <jason.vas.dias@...il.com>
Cc: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
---
 arch/x86/entry/vsyscall/vsyscall_gtod.c | 6 ++++++
 arch/x86/include/asm/vgtod.h            | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_gtod.c b/arch/x86/entry/vsyscall/vsyscall_gtod.c
index 64b1e7c..402c3b3 100644
--- a/arch/x86/entry/vsyscall/vsyscall_gtod.c
+++ b/arch/x86/entry/vsyscall/vsyscall_gtod.c
@@ -69,6 +69,12 @@ void update_vsyscall(struct timekeeper *tk)
 	base->mult = tk->tkr_mono.mult;
 	base->shift = tk->tkr_mono.shift;
 
+	base = &vdata->basetime[CLOCK_MONOTONIC_RAW];
+	base->sec = tk->raw_sec;
+	base->nsec = tk->tkr_raw.xtime_nsec;
+	base->mult = tk->tkr_raw.mult;
+	base->shift = tk->tkr_raw.shift;
+
 	base = &vdata->basetime[CLOCK_REALTIME_COARSE];
 	base->sec = tk->xtime_sec;
 	base->nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index b1f6df3..1fb7048 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -30,7 +30,8 @@ struct vgtod_ts {
 };
 
 #define VGTOD_BASES	(CLOCK_TAI + 1)
-#define VGTOD_HRES	(BIT(CLOCK_REALTIME) | BIT(CLOCK_MONOTONIC) | BIT(CLOCK_TAI))
+#define VGTOD_HRES	(BIT(CLOCK_REALTIME) | BIT(CLOCK_MONOTONIC) | \
+			 BIT(CLOCK_MONOTONIC_RAW) | BIT(CLOCK_TAI))
 #define VGTOD_COARSE	(BIT(CLOCK_REALTIME_COARSE) | BIT(CLOCK_MONOTONIC_COARSE))
 
 /*
-- 
2.4.6