From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id B5BA13858023 for ; Thu, 29 Jul 2021 08:20:52 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org B5BA13858023 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-511-M5QA0vqpMEqKein2r_Ia7Q-1; Thu, 29 Jul 2021 04:20:50 -0400 X-MC-Unique: M5QA0vqpMEqKein2r_Ia7Q-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AA6725A069; Thu, 29 Jul 2021 08:20:49 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-7.ams2.redhat.com [10.36.112.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9228A69CBA; Thu, 29 Jul 2021 08:20:48 +0000 (UTC) From: Florian Weimer To: Christian Weiss Cc: "libc-help@sourceware.org" , Felix Uhl Subject: Re: Runtime discrepancy clock_gettime + funcition instrumentation References: <5175db58f09c413b9c652d5dc45a2248@EUX13SRV2.EU.NEC.COM> <87fsvx60f0.fsf@oldenburg.str.redhat.com> Date: Thu, 29 Jul 2021 10:20:46 +0200 In-Reply-To: (Christian Weiss's message of "Thu, 29 Jul 2021 08:18:31 +0000") Message-ID: <87zgu54jkx.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-help@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-help mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 Jul 2021 08:20:53 -0000 * Christian Weiss: > Dear Florian, > > Thank you for the quick reply. As far as I understand, I can check if vdso is used by using strace on the binary. Doing so I get: > > ```[cweiss@amd022 overhead]$ strace ./test_time_static_gcc.x 1 2>&1 | grep -i clock_gettime > clock_gettime(CLOCK_MONOTONIC, {tv_sec=89045, tv_nsec=95268751}) = 0 > clock_gettime(CLOCK_MONOTONIC, {tv_sec=89145, tv_nsec=95813405}) = 0 > clock_gettime(CLOCK_MONOTONIC, {tv_sec=89145, tv_nsec=95863144}) = 0 > clock_gettime(CLOCK_MONOTONIC, {tv_sec=89145, tv_nsec=95933573}) = 0 > [cweiss@amd022 overhead]$ strace ./test_time_dyn_gcc.x 1 2>&1 | grep -i clock_gettime``` > > Am I right that this implies that vdso is not used in the static > binary, but in the dynamic one? Is there a way to activate it in the > static case or do I just have to live with that? Later glibc versions support vDSO in static binaries. glibc 2.17 as used by Red Hat Enterprise Linux 7 apparently does not. (Your observations match my recollections, but I haven't double-checked them.) Thanks, Florian