From mboxrd@z Thu Jan 1 00:00:00 1970 From: Namhyung Kim Subject: Re: Question about LLC-load-misses event Date: Tue, 23 Oct 2012 14:39:54 +0900 Message-ID: <87a9vd7nmd.fsf@sejong.aot.lge.com> References: <507C0A9F.8060405@core.kaist.ac.kr> <507C1036.7020707@core.kaist.ac.kr> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from [156.147.1.121] ([156.147.1.121]:42655 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752711Ab2JWFkQ convert rfc822-to-8bit (ORCPT ); Tue, 23 Oct 2012 01:40:16 -0400 In-Reply-To: <507C1036.7020707@core.kaist.ac.kr> (Chulmin Kim's message of "Mon, 15 Oct 2012 22:31:34 +0900") Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Chulmin Kim Cc: linux-perf-users@vger.kernel.org Hi Chulmin, On Mon, 15 Oct 2012 22:31:34 +0900, Chulmin Kim wrote: > 2012-10-15 =EC=98=A4=ED=9B=84 10:07, Chulmin Kim =EC=93=B4 =EA=B8=80: >> (perf command : perf stat -a -A -e LLC-loads -e LLC-load-misses -e >> instructions sleep 3) >> >> The problem is,, the bandwidth from STREAM benchmark does not match = with >> the monitored value. >> >> e.g. >> I got 9395MB/s from Stream. >> >> "perf" shows 134,642,063 LLC-load-misses for 3 seconds. >> -> BW =3D ((# of events)/(3 seconds)) * 64 bytes / (1024*1024) =3D 2= 739MB/s >> In this equation, the term (64bytes) is for cache line size, and the >> term(1024*1024) is for (MB/s). >> >> Why does this mismatch occur? > In case of Oprofile, the value for a certain event represents the num= ber > of the overflows which occur when the number of the event exceeds the > predefined value. > Is it a similar case with that? I guess not. And what's the result of the LLC-loads? AFAIK it counts all cache accesses including hits and misses. Did you calculate the bandwidth using the result of LLC-loads? I suspect the h/w *might* prefetches a couple of lines when cache-miss occurred, but I'm not sure. :) Thanks, Namhyung