From: Pavel Tatashin <pasha.tatashin@oracle.com>
To: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
linux@armlinux.org.uk, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, john.stultz@linaro.org,
sboyd@codeaurora.org, x86@kernel.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de, hpa@zytor.com, douly.fnst@cn.fujitsu.com,
peterz@infradead.org, prarit@redhat.com, feng.tang@intel.com,
pmladek@suse.com, gnomes@lxorguk.ukuu.org.uk,
linux-s390@vger.kernel.org, pasha.tatashin@oracle.com,
boris.ostrovsky@oracle.com, jgross@suse.com
Subject: [PATCH v13 10/18] time: default boot time offset to local_clock()
Date: Wed, 11 Jul 2018 20:04:11 -0400 [thread overview]
Message-ID: <20180712000419.5165-11-pasha.tatashin@oracle.com> (raw)
In-Reply-To: <20180712000419.5165-1-pasha.tatashin@oracle.com>
read_persistent_wall_and_boot_offset() is called during boot to read
both the persistent clock and also return the offset between the boot time
and the value of persistent clock.
Change the default boot_offset from zero to local_clock() so architectures,
that do not have a dedicated boot_clock but have early sched_clock(), such
as SPARCv9, x86, and possibly more will benefit from this change by getting
a better and more consistent estimate of the boot time without need for an
arch specific implementation.
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
kernel/time/timekeeping.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index cb738f825c12..30d7f64ffc87 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1503,14 +1503,17 @@ void __weak read_persistent_clock64(struct timespec64 *ts64)
* Weak dummy function for arches that do not yet support it.
* wall_time - current time as returned by persistent clock
* boot_offset - offset that is defined as wall_time - boot_time
- * default to 0.
+ * The default function calculates offset based on the current value of
+ * local_clock(). This way architectures that support sched_clock() but don't
+ * support dedicated boot time clock will provide the best estimate of the
+ * boot time.
*/
void __weak __init
read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
struct timespec64 *boot_offset)
{
read_persistent_clock64(wall_time);
- *boot_offset = (struct timespec64){0};
+ *boot_offset = ns_to_timespec64(local_clock());
}
/* Flag for if timekeeping_resume() has injected sleeptime */
--
2.18.0
next prev parent reply other threads:[~2018-07-12 0:07 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-12 0:04 [PATCH v13 00/18] Early boot time stamps Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 01/18] x86: text_poke() may access uninitialized struct pages Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 02/18] x86: initialize static branching early Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 03/18] x86/CPU: Call detect_nopl() only on the BSP Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 04/18] x86/tsc: redefine notsc to behave as tsc=unstable Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 05/18] kvm/x86: remove kvm memblock dependency Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 06/18] x86/xen/time: initialize pv xen time in init_hypervisor_platform Pavel Tatashin
2018-07-13 1:57 ` Pavel Tatashin
2018-07-17 15:28 ` Boris Ostrovsky
2018-07-18 1:38 ` Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 07/18] x86/xen/time: output xen sched_clock time from 0 Pavel Tatashin
2018-07-17 15:43 ` Boris Ostrovsky
2018-07-18 1:59 ` Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 08/18] s390/time: add read_persistent_wall_and_boot_offset() Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 09/18] time: replace read_boot_clock64() with read_persistent_wall_and_boot_offset() Pavel Tatashin
2018-07-12 0:04 ` Pavel Tatashin [this message]
2018-07-12 0:04 ` [PATCH v13 11/18] s390/time: remove read_boot_clock64() Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 12/18] ARM/time: " Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 13/18] x86/tsc: calibrate tsc only once Pavel Tatashin
2018-07-13 7:22 ` Dou Liyang
2018-07-13 11:30 ` Pavel Tatashin
2018-07-16 9:32 ` Dou Liyang
2018-07-16 13:35 ` Pavel Tatashin
2018-07-17 8:59 ` Dou Liyang
2018-07-17 14:36 ` Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 14/18] x86/tsc: initialize cyc2ns when tsc freq. is determined Pavel Tatashin
2018-07-13 9:11 ` Dou Liyang
2018-07-13 11:39 ` Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 15/18] x86/tsc: use tsc early Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 16/18] sched: move sched clock initialization and merge with generic clock Pavel Tatashin
2018-07-12 23:50 ` kbuild test robot
2018-07-12 0:04 ` [PATCH v13 17/18] sched: early boot clock Pavel Tatashin
2018-07-12 0:04 ` [PATCH v13 18/18] sched: use static key for sched_clock_running Pavel Tatashin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180712000419.5165-11-pasha.tatashin@oracle.com \
--to=pasha.tatashin@oracle.com \
--cc=boris.ostrovsky@oracle.com \
--cc=daniel.m.jordan@oracle.com \
--cc=douly.fnst@cn.fujitsu.com \
--cc=feng.tang@intel.com \
--cc=gnomes@lxorguk.ukuu.org.uk \
--cc=heiko.carstens@de.ibm.com \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=prarit@redhat.com \
--cc=sboyd@codeaurora.org \
--cc=schwidefsky@de.ibm.com \
--cc=steven.sistare@oracle.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).