linux-kernel - Re: [PATCH 1/3 v4] perf/x86/intel/uncore: Cache logical pkg id in uncore driver

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Message-ID: <alpine.DEB.2.20.1711011727080.1942@nanos>
Date:   Wed, 1 Nov 2017 17:30:31 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Prarit Bhargava <prarit@...hat.com>
cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Piotr Luc <piotr.luc@...el.com>,
        Kan Liang <kan.liang@...el.com>, Borislav Petkov <bp@...e.de>,
        Stephane Eranian <eranian@...gle.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Mathias Krause <minipli@...glemail.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH 1/3 v4] perf/x86/intel/uncore: Cache logical pkg id in
 uncore driver

On Wed, 25 Oct 2017, Prarit Bhargava wrote:

> From: Andi Kleen <ak@...ux.intel.com>
> 
> The SNB-EP uncore driver is the only user of topology_phys_to_logical_pkg
> in a performance critical path. Change it query the logical pkg ID
> only once at initialization time and then cache it in box structure.

That second sentence needs some care:

  Avoid the lookup in the hotpath and cache the id at initialization
  time. This is also a prerequisite to change the underlying logical
  package management implementation w/o impacting this driver.

Other than that.

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>