From: Alexander Sverdlin <[email protected]>
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 code ----
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#define CLOCK_TYPE CLOCK_MONOTONIC_RAW
#define DURATION_SEC 10
int main(int argc, char **argv)
{
struct timespec t, end;
unsigned long long cnt = 0;
clock_gettime(CLOCK_TYPE, &end);
end.tv_sec += DURATION_SEC;
do {
clock_gettime(CLOCK_TYPE, &t);
++cnt;
} while (t.tv_sec < end.tv_sec || t.tv_nsec < end.tv_nsec);
dprintf(STDOUT_FILENO, "%llu", cnt);
return EXIT_SUCCESS;
}
-------------------
The results from the above test program:
Clock Before After Diff
----- ------ ----- ----
CLOCK_MONOTONIC 355531720 338039373 -5%
CLOCK_MONOTONIC_RAW 44831738 336064912 +650%
CLOCK_REALTIME 347665133 338102907 -3%
Link: https://lore.kernel.org/patchwork/patch/933583/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=198961
Cc: Thomas Gleixner <[email protected]>
Cc: Jason Vas Dias <[email protected]>
Signed-off-by: Alexander Sverdlin <[email protected]>
---
arch/x86/entry/vdso/vclock_gettime.c | 11 +++++++++--
arch/x86/entry/vsyscall/vsyscall_gtod.c | 6 ++++++
arch/x86/include/asm/vgtod.h | 5 ++++-
3 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/arch/x86/entry/vdso/vclock_gettime.c
b/arch/x86/entry/vdso/vclock_gettime.c
index 98c7d12..7c9db26 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -144,6 +144,13 @@ notrace static int do_hres(clockid_t clk, struct timespec
*ts)
struct vgtod_ts *base = >od->basetime[clk];
u64 cycles, last, sec, ns;
unsigned int seq;
+ u32 mult = gtod->mult;
+ u32 shift = gtod->shift;
+
+ if (clk == CLOCK_MONOTONIC_RAW) {
+ mult = gtod->raw_mult;
+ shift = gtod->raw_shift;
+ }
do {
seq = gtod_read_begin(gtod);
@@ -153,8 +160,8 @@ notrace static int do_hres(clockid_t clk, struct timespec
*ts)
if (unlikely((s64)cycles < 0))
return vdso_fallback_gettime(clk, ts);
if (cycles > last)
- ns += (cycles - last) * gtod->mult;
- ns >>= gtod->shift;
+ ns += (cycles - last) * mult;
+ ns >>= shift;
sec = base->sec;
} while (unlikely(gtod_read_retry(gtod, seq)));
diff --git a/arch/x86/entry/vsyscall/vsyscall_gtod.c
b/arch/x86/entry/vsyscall/vsyscall_gtod.c
index cfcdba0..a967f02 100644
--- a/arch/x86/entry/vsyscall/vsyscall_gtod.c
+++ b/arch/x86/entry/vsyscall/vsyscall_gtod.c
@@ -46,11 +46,17 @@ void update_vsyscall(struct timekeeper *tk)
vdata->mask = tk->tkr_mono.mask;
vdata->mult = tk->tkr_mono.mult;
vdata->shift = tk->tkr_mono.shift;
+ vdata->raw_mult = tk->tkr_raw.mult;
+ vdata->raw_shift = tk->tkr_raw.shift;
base = &vdata->basetime[CLOCK_REALTIME];
base->sec = tk->xtime_sec;
base->nsec = tk->tkr_mono.xtime_nsec;
+ base = &vdata->basetime[CLOCK_MONOTONIC_RAW];
+ base->sec = tk->raw_sec;
+ base->nsec = tk->tkr_raw.xtime_nsec;
+
base = &vdata->basetime[CLOCK_TAI];
base->sec = tk->xtime_sec + (s64)tk->tai_offset;
base->nsec = tk->tkr_mono.xtime_nsec;
diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 913a133..f65c42b 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -28,7 +28,8 @@ 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))
/*
@@ -43,6 +44,8 @@ struct vsyscall_gtod_data {
u64 mask;
u32 mult;
u32 shift;
+ u32 raw_mult;
+ u32 raw_shift;
struct vgtod_ts basetime[VGTOD_BASES];
--
2.4.6
