From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp03.au.ibm.com (e23smtp03.au.ibm.com [202.81.31.145]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 0167B1A0A96 for ; Tue, 3 Feb 2015 14:08:33 +1100 (AEDT) Received: from /spool/local by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 3 Feb 2015 13:08:32 +1000 Received: from d23relay10.au.ibm.com (d23relay10.au.ibm.com [9.190.26.77]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id 4CEF62CE8050 for ; Tue, 3 Feb 2015 14:08:29 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay10.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t1338KBL35848204 for ; Tue, 3 Feb 2015 14:08:29 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t1337t16018609 for ; Tue, 3 Feb 2015 14:07:55 +1100 From: "Aneesh Kumar K.V" To: Anton Blanchard Subject: Re: [PATCH] powerpc/mm: Add trace point for tracking hash pte fault In-Reply-To: <20150203090129.5e3c7494@kryten> References: <1421753750-17135-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1421809627.4900.1.camel@ellerman.id.au> <87d268v7xm.fsf@linux.vnet.ibm.com> <1422425467.11009.2.camel@ellerman.id.au> <20150202212607.7585dedb@kryten> <87vbjk707w.fsf@linux.vnet.ibm.com> <20150203090129.5e3c7494@kryten> Date: Tue, 03 Feb 2015 08:37:35 +0530 Message-ID: <87pp9r7kw8.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Cc: linuxppc-dev@lists.ozlabs.org, paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Anton Blanchard writes: > Hi Aneesh, > >> yes. We do use jump label. I also verified that looking at .s >> >> #APP >> # 23 "./arch/powerpc/include/asm/jump_label.h" 1 >> 1: >> nop >> .pushsection __jump_table, "aw" >> .llong 1b, .L201, __tracepoint_hash_fault+8 #, >> .popsection >> >> # 0 "" 2 > > So we insert a single nop, and the slow path is in another section. I'd > be surprised if we could measure this, unless the nop causes a branch > target alignment issue the slow path caused some hot path icache layout > issues. > >> Without patch >> sys: 0m11.2425 >> >> With patch: >> sys: 0m11.3258 >> >> ie, a -0.7% impact >> >> If that impact is high we could possibly put that tracepoint within >> #ifdef CONFIG_DEBUG_VM ? > > Did the real time change? I'd be careful about comparing based on > system time. Yes it did. 11.8769 with patch 11.7924 without patch I will look at the perf stat data difference between the both runs and update. -aneesh