From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751101AbdAXVxS (ORCPT ); Tue, 24 Jan 2017 16:53:18 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:56791 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751218AbdAXVvo (ORCPT ); Tue, 24 Jan 2017 16:51:44 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, Matt Fleming , Mel Gorman , "Paul E. McKenney" Subject: [PATCH v3 tip/core/rcu 14/18] rcu: Enable RCU tracepoints by default to aid in debugging Date: Tue, 24 Jan 2017 13:51:25 -0800 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170124215111.GB2269@linux.vnet.ibm.com> References: <20170124215111.GB2269@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17012421-0020-0000-0000-00000B2B36F9 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006492; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000200; SDB=6.00812181; UDB=6.00396064; IPR=6.00589599; BA=6.00005085; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014031; XFM=3.00000011; UTC=2017-01-24 21:51:37 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17012421-0021-0000-0000-0000597E9960 Message-Id: <1485294689-11485-14-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-24_17:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1701240129 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Matt Fleming While debugging a performance issue I needed to understand why RCU sofitrqs were firing so frequently. Unfortunately, the RCU callback tracepoints are hidden behind CONFIG_RCU_TRACE which defaults to off in the upstream kernel and is likely to also be disabled in enterprise distribution configs. Enable it by default for CONFIG_TREE_RCU. However, we must keep it disabled for tiny RCU, because it would otherwise pull in a large amount of code that would make tiny RCU less than tiny. I ran some file system metadata intensive workloads (git checkout, FS-Mark) on a variety of machines with this patch and saw no detectable change in performance. Cc: Mel Gorman Signed-off-by: Matt Fleming Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- lib/Kconfig.debug | 1 + 1 file changed, 1 insertion(+) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index b06848a104e6..5655bd95919a 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1450,6 +1450,7 @@ config RCU_CPU_STALL_TIMEOUT config RCU_TRACE bool "Enable tracing for RCU" depends on DEBUG_KERNEL + default y if TREE_RCU select TRACE_CLOCK help This option provides tracing in RCU which presents stats -- 2.5.2