From mboxrd@z Thu Jan 1 00:00:00 1970 From: Akos Marton Subject: Re: time system call expensive? Date: Thu, 21 Jul 2011 13:46:17 +0200 Message-ID: <4E281189.8010904@gmail.com> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------060107020008070208030404" Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=message-id:disposition-notification-to:date:from:user-agent :mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:content-type; bh=3GKkmkEZXyPE0JSLefPoRUzD9kBJuzpM10N1dOMW5+8=; b=DkCpCNbG2S3hnngDUFUaRkUom5nn00GaY0W9vS2advObgmkBlzlU1Kpa5jj3l/i2vj /qCmLrgc0wYulYDZsF6hT4ysN/yRIFG9/rxwGWbxq7tpszLbOX7iRRrsimiV5Us0VXIe p9sN961gqRgKbgHZXVgKO4UL0l/NCH02lFJZo= In-Reply-To: Sender: linux-c-programming-owner@vger.kernel.org List-ID: To: Michal Nazarewicz Cc: linux-c-programming This is a multi-part message in MIME format. --------------060107020008070208030404 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit I advice you `man 3 clock`. If you want to get much more precision the attached project can help you. Does it help? Regards, mAkos Michal Nazarewicz wrote: > On Thu, 21 Jul 2011 06:41:14 +0200, Vadiraj wrote: >> I'm evaluating time consumed by method. I'm using time(NULL) system >> call to capture time before and after the call to the function. >> Just wanted to know if this has a considerable performance hit? For >> all I believe time syscall is quite optimized and should not really be >> matter of concern. >> >> Please let me know if someone have evaluated time(NULL) system over head.. >> >> Assuming the method I'm evaluating is a frequently called method. > > Why do you worry about it? What do you need the time for? If are > really using time(2) it means that the function you're calling run time > is counted in seconds. If that's the case, two call to time(2) are > by all means negligible. > > If you need in for benchmark, you would probably do something like: > > start = time(NULL) > for (vary big number) > call function you benchmark > end = time(NULL) > > In either case, you should check gettimeofday(2). > --------------060107020008070208030404 Content-Type: application/octet-stream; name="timing.tar.bz2" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="timing.tar.bz2" QlpoOTFBWSZTWUXZikUAAW//hMy4AIBef/+ff//e1P/v/2oAAIAIUARe4zsrp2Ns07bsIZFG QjSbSbJoTJppo9Q0HqGgyBpoAyA0ANNSFPT0aNU9NJhGagAeoZGIGIBkNNNNDIBIkEEyNApt U/VPSfqj/VTyIPKHqMjRoep6gAADyhxkyaNAaNMRkaGIYE0aYgxGgwgAMEkUJ6AKm0wp7U9J 6poABoyPUBk9QGnqbSaaeoeptOkTQ6OZvrmLbxl+hQlZkA04hCv7F/A5HKKwUgvKC1kvYndY FrGC8QmkKAXPhvbaD4/l65IzpAhtMab7u8/Hv91v7TBdT/hUJ0UUgbGUijt7NlLv0z/mZj5R 6r9HR8XSU9RkMu0twjjpn05KVNBugqnUdAoEwA4BPnBoiV+Nq+uZWfK22q9fdlq5zZwe8GgB uIs1IszZ5G2ppcgdHQyhLqVbQEyCPLbsoopHIrl36Ss5i5Io6jj2nNU0rD1AT7E07XaSnVOR VS6s6qoWGFkLH32sU8KCCJZnHTu09ZZ5TwkuY9xJzUShDaKAw5ZrDmlETRyeeulI9KSuKxDC JbTlb2POrzhXV0vsZyuIvy/zqhcDz2YMJBRcG2kgj36MVI8QcSAJTIBKJRbf8LAjrvlqBR7X ID0YGPwSssymcLdwdt+NzKTrHcJtlA+YWIg3HUzgg16/v+PVv5xBAWQTicWIW9HbVY9ZxEqU wtIoL2dzgTFSt/oKJMhiwkQW7trsPsreKWJOd982FbihEI0m8lUDC0VgovNQN6KE3QUzOaxe n5rleo6IyuIiS+9GkCCmkWGw4GoyfCIQYUPCiBP3+9Bj5ZvyHl4g7QelLj6Lk9cIM2gd5FAM Bg1GswqBSTi9uwwJcIR9JQbOrZ+5ZBokuoNIbnk5lNsFsR7g3SIqiISBMRhmxs0lovhU6RdH bCCksLi7VMOYijOWB49v3FkKIezKUxatXbxW3gbbZhxFlXzIbhthAUKyVyZBLEgolsgkIjNI KVxnj1ni8jcpphYQZ8cEF4wrNNskGp96B1op0bWs+lphFKTy1z88Q7gDVnCozj4EEvZKJaNT ocYyvuki56SPvDoxNZvFOVJSYeU4t2kwmMljFRh0WTsHwkvAZZ2PENPN29avxelOrfAnL8+Y MjMO6c0jDkVzEuJkrWTRjgEYyeQzofx1azrVsNUllRkDJaWY1PM7ooAV+0lUhUWYVKWUCBrJ pA4QWvpKUDcD0sEsgAiEe4zUSVCTLgosnwJSNeK4XXLCuuvkFcTaQrBVIgGSiF4ioTlw7ojG SRa7DiGO/XWYXZqDOluNNT4KED4S2+DYLboLHwWSgVjCS6UF7nicsq0gVrmvdXRYVrqomYNG zZ6efPoftyG5l8GdvtZWmie2XIg7xOgGSrkLZxPZ8lEBVQO/nAg6ZC37M8ok5Y81NEhYW4Lh inp0HF+N1FakZX2zW2eBjaStX0NcklSlGbyV1y0A7dW9b1daWGJLwFLZJawrCPVjqlqdznQD +4I2iQf8XckU4UJBF2YpFA== --------------060107020008070208030404--