From: "\"Jan H. Schönherr\"" <jschoenh@amazon.de>
To: Len Brown <lenb@kernel.org>, Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Anthony Liguori <aliguori@amazon.com>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Tim Deegan <tim@xen.org>, Gang Wei <gang.wei@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: native_cpu_up speed (Re: [PATCH] x86: skip delays during SMP initialization similar to Xen)
Date: Fri, 29 May 2015 10:04:43 +0200 [thread overview]
Message-ID: <55681D9B.2040903@amazon.de> (raw)
In-Reply-To: <CAJvTdKmz9105cYDiZThfCd29PWeNh2d2QbZFZ0n_UEeqCah7Fg@mail.gmail.com>
On 05/29/2015 09:47 AM, Len Brown wrote:
> However, a clear pattern jumped out of the trace for how long
> the BSP waits for the AP to set itself in cpu_callin_mask.
> This is the time in start secondary where cpu_init() is running,
> up through smp_callin() is called.
>
> On the 1st package, each remote AP take 9 delays = 900 us to do this,
> whether they are new cores or HT siblings of cores already up.
> But the 1st processor on remote_packages_ aka nodes, takes 60,000 us
>
> No typo -- that is 60ms!
That does sound like calibrate_delay(), which "waits" for 5 * (10ms + 1 tick)
on each newly encountered package...
Regards
Jan
prev parent reply other threads:[~2015-05-29 8:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-29 7:47 native_cpu_up speed (Re: [PATCH] x86: skip delays during SMP initialization similar to Xen) Len Brown
2015-05-29 8:04 ` "Jan H. Schönherr" [this message]
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