From: "Adam C. Emerson" <aemerson@redhat.com>
To: Erwan Velu <evelu@redhat.com>
Cc: The Sacred Order of the Squid Cybernetic <ceph-devel@vger.kernel.org>
Subject: Re: About ceph_clock_now()
Date: Wed, 13 Jan 2016 10:28:16 -0500 [thread overview]
Message-ID: <20160113152816.GB24712@ultraspiritum.redhat.com> (raw)
In-Reply-To: <964746730.10566211.1452681675142.JavaMail.zimbra@redhat.com>
On 13/01/2016, Erwan Velu wrote:
[snip]
> You consider the MONOTONIC clock drifting a lot ?
> I mean an NTP adjustement can make a serious jump forward or even worse backward.
So, CLOCK_MONOTONIC will never jump backward (thus the name). And there
is a system-defined limit on how much it will ever jump forward at any
given time, though I don't know what that value is offhand. On a
well-synchronized system, at least it should give more accurate durations than
CLOCK_MONOTONIC_RAW. That said, if you're coming up from a cold boot and you're
out of sync, it could be jumpier. As I said, I am not a Timelord, this is just
what I've gathered as received wisdom.
[snip]
> You mean we could switch some of ceph_clock_now() calls to ceph_time ?
> We could use coarse_mono_clock to perform that.
>
> If you agree that switching code like the one I'm speaking is valuable, I can work on it.
I think that would be very valuable, thank you.
--
Senior Software Engineer Red Hat Storage, Ann Arbor, MI, US
IRC: Aemerson@{RedHat, OFTC, Freenode}
0x80F7544B90EDBFB9 E707 86BA 0C1B 62CC 152C 7C12 80F7 544B 90ED BFB9
prev parent reply other threads:[~2016-01-13 15:28 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <177186823.10053087.1452614184109.JavaMail.zimbra@redhat.com>
2016-01-12 15:59 ` About ceph_clock_now() Erwan Velu
2016-01-12 17:32 ` Adam C. Emerson
2016-01-13 10:41 ` Erwan Velu
2016-01-13 13:48 ` Sage Weil
2016-01-13 14:52 ` Matt Benjamin
2016-01-14 16:10 ` Erwan Velu
2016-01-14 16:14 ` Adam C. Emerson
2016-01-19 16:17 ` Erwan Velu
2016-01-19 16:29 ` Adam C. Emerson
2016-01-19 16:57 ` Erwan Velu
2016-01-21 19:22 ` Erwan Velu
2016-01-22 16:00 ` Erwan Velu
2016-01-22 17:35 ` Adam C. Emerson
2016-01-26 14:12 ` Erwan Velu
2016-01-23 11:49 ` Willem Jan Withagen
2016-01-23 20:20 ` Matt Benjamin
2016-01-23 21:55 ` Adam C. Emerson
2016-01-24 11:53 ` Willem Jan Withagen
2016-01-24 12:51 ` Willem Jan Withagen
2016-01-25 0:03 ` Adam C. Emerson
2016-01-25 9:08 ` Willem Jan Withagen
2016-01-25 9:58 ` Erwan Velu
2016-01-25 10:57 ` Willem Jan Withagen
2016-01-25 17:22 ` Adam C. Emerson
[not found] ` <56A66099.4030501@digiware.nl>
[not found] ` <1523354716.24670379.1453744826329.JavaMail.zimbra@redhat.com>
2016-01-25 19:38 ` Willem Jan Withagen
2016-01-25 20:14 ` Adam C. Emerson
2016-01-25 20:18 ` Matt Benjamin
2016-01-25 20:22 ` Willem Jan Withagen
2016-01-13 15:28 ` Adam C. Emerson [this message]
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