linux-kernel - Re: [PATCH] x86/topology: Fallback to SMT level only once

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Message-ID: <20160829104047.GH10153@twins.programming.kicks-ass.net>
Date:   Mon, 29 Aug 2016 12:40:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Jean-Pierre Lozi <jplozi@...ce.fr>,
        Jirka Hladky <jhladky@...hat.com>,
        Petr Surý <psury@...hat.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/topology: Fallback to SMT level only once

On Sun, Aug 28, 2016 at 08:19:46PM +0200, Jiri Olsa wrote:
> Jirka, Peter and Jean-Pierre reported performance drop on
> some cpus after making cpu offline and online again.
> 
> The reason is the kernel logic that falls back to SMT
> level topology if more than one node is detected within
> CPU package. During the system boot this logic cuts out
> the DIE topology level and numa code adds NUMA level
> on top of this.

Its not SMT topology, and back when I asked if he had CoD enabled or
such he said not.


See also:

http://lkml.kernel.org/r/1471559812-19967-3-git-send-email-srinivas.pandruvada@linux.intel.com

Arguably, that should have been split in two patches, but alas..