xen-devel.lists.xenproject.org archive mirror
 help / color / mirror / Atom feed
From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
	xen-devel <xen-devel@lists.xenproject.org>
Cc: Dario Faggioli <dario.faggioli@citrix.com>,
	Joao Martins <joao.m.martins@oracle.com>
Subject: Re: [PATCH 1/8] x86/time: improve cross-CPU clock monotonicity (and more)
Date: Tue, 2 Aug 2016 20:30:15 +0100	[thread overview]
Message-ID: <8efd4ae7-723e-ecf1-5a8c-6ace41cc12d3@citrix.com> (raw)
In-Reply-To: <5761496802000078000F5395@prv-mh.provo.novell.com>


[-- Attachment #1.1: Type: text/plain, Size: 1217 bytes --]

On 15/06/16 11:26, Jan Beulich wrote:
> Using the bare return value from read_platform_stime() is not suitable
> when local_time_calibration() is going to use its fast path: Divergence
> of several dozen microseconds between NOW() return values on different
> CPUs results when platform and local time don't stay in close sync.
>
> Latch local and platform time on the CPU initiating AP bringup, such
> that the AP can use these values to seed its stime_local_stamp with as
> little of an error as possible. The boot CPU, otoh, can simply
> calculate the correct initial value (other CPUs could do so too with
> even greater accuracy than the approach being introduced, but that can
> work only if all CPUs' TSCs start ticking at the same time, which
> generally can't be assumed to be the case on multi-socket systems).
>
> This slightly defers init_percpu_time() (moved ahead by commit
> dd2658f966 ["x86/time: initialise time earlier during
> start_secondary()"]) in order to reduce as much as possible the gap
> between populating the stamps and consuming them.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Subject to the style issue spotted by Joao, Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>

[-- Attachment #1.2: Type: text/html, Size: 1747 bytes --]

[-- Attachment #2: Type: text/plain, Size: 127 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

  parent reply	other threads:[~2016-08-02 19:30 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-15  9:50 [PATCH 0/8] x86/time: improve cross-CPU clock monotonicity (and more) Jan Beulich
2016-06-15 10:26 ` [PATCH 1/8] " Jan Beulich
2016-06-15 10:32   ` Jan Beulich
2016-06-15 22:51   ` Joao Martins
2016-06-16  8:27     ` Jan Beulich
2016-06-16 20:27       ` Joao Martins
2016-06-17  7:32         ` Jan Beulich
2016-06-21 12:05           ` Joao Martins
2016-06-21 12:28             ` Jan Beulich
2016-06-21 13:57               ` Joao Martins
2016-08-02 19:30   ` Andrew Cooper [this message]
2016-06-15 10:26 ` [PATCH 2/8] x86: also generate assembler usable equates for synthesized features Jan Beulich
2016-06-20 12:50   ` Andrew Cooper
2016-06-15 10:27 ` [PATCH 3/8] x86/time: introduce and use rdtsc_ordered() Jan Beulich
2016-06-20 12:59   ` Andrew Cooper
2016-06-20 13:06     ` Jan Beulich
2016-06-20 13:07       ` Andrew Cooper
2016-07-11 11:39     ` Dario Faggioli
2016-06-15 10:28 ` [PATCH 4/8] x86/time: calibrate TSC against platform timer Jan Beulich
2016-06-20 14:20   ` Andrew Cooper
2016-06-20 15:19     ` Jan Beulich
2016-08-02 19:25       ` Andrew Cooper
2016-08-03  9:32         ` Jan Beulich
2016-06-15 10:28 ` [PATCH 5/8] x86/time: correctly honor late clearing of TSC related feature flags Jan Beulich
2016-06-20 14:32   ` Andrew Cooper
2016-06-20 15:20     ` Jan Beulich
2016-07-04 15:39       ` Andrew Cooper
2016-07-04 15:53         ` Jan Beulich
2016-08-02 19:08           ` Andrew Cooper
2016-08-03  9:43             ` Jan Beulich
2016-08-31 13:42               ` Andrew Cooper
2016-08-31 14:03                 ` Jan Beulich
2016-06-15 10:29 ` [PATCH 6/8] x86/time: support 32-bit wide ACPI PM timer Jan Beulich
2016-07-04 15:40   ` Andrew Cooper
2016-06-15 10:30 ` [PATCH 7/8] x86/time: fold recurring code Jan Beulich
2016-07-04 15:43   ` Andrew Cooper
2016-06-15 10:30 ` [PATCH 8/8] x86/time: group time stamps into a structure Jan Beulich
2016-07-04 15:57   ` Andrew Cooper
2016-07-01  7:44 ` Ping: [PATCH 0/8] x86/time: improve cross-CPU clock monotonicity (and more) Jan Beulich

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=8efd4ae7-723e-ecf1-5a8c-6ace41cc12d3@citrix.com \
    --to=andrew.cooper3@citrix.com \
    --cc=JBeulich@suse.com \
    --cc=dario.faggioli@citrix.com \
    --cc=joao.m.martins@oracle.com \
    --cc=xen-devel@lists.xenproject.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).