From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH v4 1/3] x86/time: latch to-be-written TSC value early in rendezvous loop
Date: Tue, 20 Apr 2021 17:44:53 +0200 [thread overview]
Message-ID: <YH729WcM5Uqz9vwk@Air-de-Roger> (raw)
In-Reply-To: <35bbad56-d0f0-a37d-674c-e635eaf9c94c@suse.com>
On Thu, Apr 01, 2021 at 11:54:05AM +0200, Jan Beulich wrote:
> To reduce latency on time_calibration_tsc_rendezvous()'s last loop
> iteration, read the value to be written on the last iteration at the end
> of the loop body (i.e. in particular at the end of the second to last
> iteration).
>
> On my single-socket 18-core Skylake system this reduces the average loop
> exit time on CPU0 (from the TSC write on the last iteration to until
> after the main loop) from around 32k cycles to around 29k (albeit the
> values measured on separate runs vary quite significantly).
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Thanks, Roger.
next prev parent reply other threads:[~2021-04-20 15:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 9:53 [PATCH v4 0/3] x86/time: calibration rendezvous adjustments Jan Beulich
2021-04-01 9:54 ` [PATCH v4 1/3] x86/time: latch to-be-written TSC value early in rendezvous loop Jan Beulich
2021-04-20 15:44 ` Roger Pau Monné [this message]
2021-04-01 9:54 ` [PATCH v4 2/3] x86/time: yield to hyperthreads after updating TSC during rendezvous Jan Beulich
2021-04-20 15:59 ` Roger Pau Monné
2021-04-21 9:57 ` Jan Beulich
2021-04-01 9:55 ` [PATCH v4 3/3] x86/time: avoid reading the platform timer in rendezvous functions Jan Beulich
2021-04-20 16:12 ` Roger Pau Monné
2021-04-21 10:06 ` Jan Beulich
2021-04-29 9:32 ` Jan Beulich
2021-04-29 12:48 ` Roger Pau Monné
2021-04-29 12:53 ` Roger Pau Monné
2021-04-29 13:51 ` Jan Beulich
2021-04-15 9:54 ` Ping: [PATCH v4 0/3] x86/time: calibration rendezvous adjustments Jan Beulich
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