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Date: Wed, 8 Aug 2018 09:51:47 -0700 From: Reinette Chatre <reinette.chatre@...el.com> To: Peter Zijlstra <peterz@...radead.org>, "Luck, Tony" <tony.luck@...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 On 8/8/2018 9:47 AM, Peter Zijlstra wrote: > On Wed, Aug 08, 2018 at 03:55:54PM +0000, Luck, Tony wrote: >>> 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. > > Well, Reinette used perf_event_read_local() which is unfortunately quite > a bit. But the inline I proposed is a single load and depending on > rdpmcl() or native_read_pmc() a call to or just a single inline asm > rdpmc instruction. > > That should certainly work I think. I am in the process of testing this variation. Reinette
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