linux-kernel - RE: [PATCH 0/2] x86/intel_rdt and perf/x86: Fix lack of coordination with perf

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Date:   Wed, 8 Aug 2018 15:55:54 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>
CC:     "Hansen, Dave" <dave.hansen@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "vikas.shivappa@...ux.intel.com" <vikas.shivappa@...ux.intel.com>,
        "Hindman, Gavin" <gavin.hindman@...el.com>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 0/2] x86/intel_rdt and perf/x86: Fix lack of
 coordination with perf

> So _why_ doesn't this work? As said by Tony, that first call should
> prime the caches, so the second and third calls should not generate any
> misses.

How much code/data is involved? If there is a lot, then you may be unlucky
with cache coloring and the later parts of the "prime the caches" code path
may evict some lines loaded in the early parts.

-Tony