From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnaldo Carvalho de Melo Subject: Re: perf utility question: "Sky high iTLB-load-misses" Date: Thu, 9 Nov 2017 10:53:25 -0300 Message-ID: <20171109135325.GJ4333@kernel.org> References: <20171108163440.GA10004@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Received: from mail.kernel.org ([198.145.29.99]:53264 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751066AbdKINx2 (ORCPT ); Thu, 9 Nov 2017 08:53:28 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Andi Kleen Cc: Vince Weaver , Peter Zijlstra , Jan =?iso-8859-1?Q?Pokorn=FD?= , linux-perf-users@vger.kernel.org Em Wed, Nov 08, 2017 at 11:55:02AM -0500, Vince Weaver escreveu: > On Wed, 8 Nov 2017, Jan Pokorný wrote: > > > Is iTLB-load-misses > 100% reported because of some deficiency > > of the platform, a bug in perf, or an expected behaviour? > > If you look into the kernel, the two events being measured are > [ C(RESULT_ACCESS) ] = 0x2085, /* ITLB_MISSES.STLB_HIT */ > [ C(RESULT_MISS) ] = 0xe85, /* ITLB_MISSES.WALK_COMPLETED */ > > If you look this up in Intel Vol3b you can see that the "access" metric > measures First level ITLB misses that hit in the Second-level TLB > > Wheras the miss metric is a list of accesses from any level that caused a > walk of the page tables. > > So the events don't necessarily sound like they match up very well, so > it's beleivable you will get odd results when trying to calculate > percentages based on them. Andi, is this something you can help in figuring out a fix? Peter? - Arnaldo