From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <fweimer@redhat.com>
Received: from us-smtp-delivery-124.mimecast.com
 (us-smtp-delivery-124.mimecast.com [170.10.133.124])
 by sourceware.org (Postfix) with ESMTP id E95573938C2A
 for <libc-help@sourceware.org>; Thu, 29 Jul 2021 07:31:52 +0000 (GMT)
DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E95573938C2A
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-360-3tBmPGXZNEO0NA8qdPpHJg-1; Thu, 29 Jul 2021 03:31:51 -0400
X-MC-Unique: 3tBmPGXZNEO0NA8qdPpHJg-1
Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com
 [10.5.11.15])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4A3631008060;
 Thu, 29 Jul 2021 07:31:50 +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 320CE6A901;
 Thu, 29 Jul 2021 07:31:48 +0000 (UTC)
From: Florian Weimer <fweimer@redhat.com>
To: Christian Weiss <Christian.Weiss@EMEA.NEC.COM>
Cc: "libc-help@sourceware.org" <libc-help@sourceware.org>,  Felix Uhl
 <Felix.Uhl@EMEA.NEC.COM>
Subject: Re: Runtime discrepancy clock_gettime + funcition instrumentation
References: <5175db58f09c413b9c652d5dc45a2248@EUX13SRV2.EU.NEC.COM>
Date: Thu, 29 Jul 2021 09:31:47 +0200
In-Reply-To: <5175db58f09c413b9c652d5dc45a2248@EUX13SRV2.EU.NEC.COM>
 (Christian Weiss's message of "Thu, 29 Jul 2021 07:26:14 +0000")
Message-ID: <87fsvx60f0.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 10.5.11.15
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_H4, 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 <libc-help.sourceware.org>
List-Unsubscribe: <https://sourceware.org/mailman/options/libc-help>,
 <mailto:libc-help-request@sourceware.org?subject=unsubscribe>
List-Archive: <https://sourceware.org/pipermail/libc-help/>
List-Help: <mailto:libc-help-request@sourceware.org?subject=help>
List-Subscribe: <https://sourceware.org/mailman/listinfo/libc-help>,
 <mailto:libc-help-request@sourceware.org?subject=subscribe>
X-List-Received-Date: Thu, 29 Jul 2021 07:31:54 -0000

* Christian Weiss:

> Measuring the runtime, the static binary takes about five times more time to finish than the dynamic one. I do not yet understand this observation:
>
> [cweiss@amd022 overhead]$ time ./test_time_static_gcc.x 10000000
> sum: 49999995000000
> real         0m2.594s
> user        0m0.396s
> sys           0m2.197s
> [cweiss@amd022 overhead]$ time ./test_time_dyn_gcc.x 10000000
> sum: 49999995000000
>
> real         0m0.518s
> user        0m0.515s
> sys           0m0.002s

Have you checked that the statically linked version uses vDSO
acceleration instead of system calls?

Thanks,
Florian