From: Nicolai Stange <nicstange@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>,
linux-kernel@vger.kernel.org,
Nicolai Stange <nicstange@gmail.com>
Subject: [RFC v6 18/23] clockevents: min delta increment: calculate min_delta_ns from ticks
Date: Fri, 9 Sep 2016 22:18:07 +0200 [thread overview]
Message-ID: <20160909201812.32396-3-nicstange@gmail.com> (raw)
In-Reply-To: <20160909200033.32103-1-nicstange@gmail.com>
The use of a clockevent device's ->min_delta_ns in the event programming
path hinders upcoming changes to the clockevent core making it NTP
correction aware: both, ->mult and ->min_delta_ns would need to get
updated as well as consumed atomically and we'd rather like to avoid any
locking here.
We already have got ->min_delta_ticks_adjusted which
- resembles the value of ->min_delta_ns
- and is guaranteed to be always >= the hardware's hard limit
->min_delta_ticks and thus, can be used w/o locking as we don't care
for small deviations.
In clockevents_increase_min_delta(), don't use ->min_delta_ns but
calculate it dynamically from ->min_delta_ticks_adjusted.
As clockevents_increase_min_delta() gets invoked only rarely, the
additional division should not be an issue from a performance standpoint.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---
kernel/time/clockevents.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index aa7b325..86d9f97 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -210,23 +210,26 @@ int clockevents_tick_resume(struct clock_event_device *dev)
*/
static int clockevents_increase_min_delta(struct clock_event_device *dev)
{
+ u64 min_delta_ns = cev_delta2ns(dev->min_delta_ticks_adjusted, dev,
+ false);
+
/* Nothing to do if we already reached the limit */
- if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
+ if (min_delta_ns >= MIN_DELTA_LIMIT) {
printk_deferred(KERN_WARNING
"CE: Reprogramming failure. Giving up\n");
dev->next_event.tv64 = KTIME_MAX;
return -ETIME;
}
- if (dev->min_delta_ns < 5000)
- dev->min_delta_ns = 5000;
+ if (min_delta_ns < 5000)
+ min_delta_ns = 5000;
else
- dev->min_delta_ns += dev->min_delta_ns >> 1;
+ min_delta_ns += min_delta_ns >> 1;
- if (dev->min_delta_ns > MIN_DELTA_LIMIT)
- dev->min_delta_ns = MIN_DELTA_LIMIT;
+ if (min_delta_ns > MIN_DELTA_LIMIT)
+ min_delta_ns = MIN_DELTA_LIMIT;
- dev->min_delta_ticks_adjusted = (unsigned long)((dev->min_delta_ns *
+ dev->min_delta_ticks_adjusted = (unsigned long)((min_delta_ns *
dev->mult) >> dev->shift);
dev->min_delta_ticks_adjusted = max(dev->min_delta_ticks_adjusted,
dev->min_delta_ticks);
@@ -234,7 +237,7 @@ static int clockevents_increase_min_delta(struct clock_event_device *dev)
printk_deferred(KERN_WARNING
"CE: %s increased min_delta_ns to %llu nsec\n",
dev->name ? dev->name : "?",
- (unsigned long long) dev->min_delta_ns);
+ (unsigned long long) min_delta_ns);
return 0;
}
--
2.9.3
next prev parent reply other threads:[~2016-09-09 20:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-09 20:00 [RFC v6 00/23] adapt clockevents frequencies to mono clock Nicolai Stange
2016-09-09 20:00 ` [RFC v6 01/23] clocksource: sh_cmt: compute rate before registration again Nicolai Stange
2016-09-10 12:56 ` Thomas Gleixner
2016-09-10 18:51 ` Joe Perches
2016-09-10 19:11 ` Nicolai Stange
2016-09-09 20:00 ` [RFC v6 02/23] clocksource: sh_tmu: " Nicolai Stange
2016-09-09 20:00 ` [RFC v6 03/23] clocksource: em_sti: split clock prepare and enable steps Nicolai Stange
2016-09-09 20:00 ` [RFC v6 04/23] clocksource: em_sti: compute rate before registration Nicolai Stange
2016-09-09 20:00 ` [RFC v6 05/23] clocksource: h8300_timer8: don't reset rate in ->set_state_oneshot() Nicolai Stange
2016-09-09 20:00 ` [RFC v6 06/23] clockevents: make clockevents_config() static Nicolai Stange
2016-09-09 20:00 ` [RFC v6 07/23] many clockevent drivers: set ->min_delta_ticks and ->max_delta_ticks Nicolai Stange
2016-09-09 20:00 ` [RFC v6 08/23] arch/s390/kernel/time: " Nicolai Stange
2016-09-09 20:00 ` [RFC v6 09/23] arch/x86/platform/uv/uv_time: " Nicolai Stange
2016-09-09 20:00 ` [RFC v6 10/23] arch/tile/kernel/time: " Nicolai Stange
2016-09-09 20:00 ` [RFC v6 11/23] clockevents: always initialize ->min_delta_ns and ->max_delta_ns Nicolai Stange
2016-09-09 20:00 ` [RFC v6 12/23] many clockevent drivers: don't set " Nicolai Stange
2016-09-09 20:00 ` [RFC v6 13/23] clockevents: introduce CLOCK_EVT_FEAT_NO_ADJUST flag Nicolai Stange
2016-09-09 20:00 ` [RFC v6 14/23] clockevents: decouple ->max_delta_ns from ->max_delta_ticks Nicolai Stange
2016-09-09 20:00 ` [RFC v6 15/23] clockevents: do comparison of delta against minimum in terms of cycles Nicolai Stange
2016-09-09 20:18 ` [RFC v6 16/23] clockevents: clockevents_program_min_delta(): don't set ->next_event Nicolai Stange
2016-09-09 20:18 ` [RFC v6 17/23] clockevents: use ->min_delta_ticks_adjusted to program minimum delta Nicolai Stange
2016-09-09 20:18 ` Nicolai Stange [this message]
2016-09-09 20:18 ` [RFC v6 19/23] timer_list: print_tickdevice(): calculate ->min_delta_ns dynamically Nicolai Stange
2016-09-09 20:18 ` [RFC v6 20/23] clockevents: purge ->min_delta_ns Nicolai Stange
2016-09-09 20:18 ` [RFC v6 21/23] clockevents: initial support for mono to raw time conversion Nicolai Stange
2016-09-09 20:18 ` [RFC v6 22/23] clockevents: make setting of ->mult and ->mult_adjusted atomic Nicolai Stange
2016-09-09 20:18 ` [RFC v6 23/23] timekeeping: inform clockevents about freq adjustments Nicolai Stange
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=20160909201812.32396-3-nicstange@gmail.com \
--to=nicstange@gmail.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
/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