From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe Subject: extreme ceph-osd cpu load for rand. 4k write Date: Wed, 07 Nov 2012 21:41:22 +0100 Message-ID: <509AC772.5010606@profihost.ag> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.profihost.ag ([85.158.179.208]:56911 "EHLO mail.profihost.ag" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751852Ab2KGUl0 (ORCPT ); Wed, 7 Nov 2012 15:41:26 -0500 Sender: ceph-devel-owner@vger.kernel.org List-ID: To: "ceph-devel@vger.kernel.org" Hello list, whiling benchmarking i was wondering, why the ceph-osd load is so extreme high while having random 4k write i/o. Here an example while benchmarking: random 4k write: 16.000 iop/s 180% CPU Load in top from EACH ceph-osd process random 4k read: 16.000 iop/s 19% CPU Load in top from EACH ceph-osd process seq 4M write: 800MB/s 14% CPU Load in top from EACH ceph-osd process seq 4M read: 1600MB/s 9% CPU Load in top from EACH ceph-osd process I can't understand why in this single case the load is so EXTREMELY high. Greets Stefan