From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail.logilab.fr ([213.215.7.51]:38552 "EHLO tucana.logilab.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342AbbAMQoA (ORCPT ); Tue, 13 Jan 2015 11:44:00 -0500 Date: Tue, 13 Jan 2015 17:36:19 +0100 From: Julien Cristau To: Trond Myklebust , linux-nfs@vger.kernel.org Cc: David Douard Subject: nfs client stat() performance degradation Message-ID: <20150113163618.GA17059@sh76.dev.logilab.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-nfs-owner@vger.kernel.org List-ID: Hi, we're experiencing some troubling performance issues with our nfs clients. One of the symptoms is degraded performance of directory walks with hot caches and expired attribute caches: "find -ls" in the kernel tree goes from about 4s (cold caches) to 1.5s (hot vm caches) and then to 18s after actimeo. Network traffic increases by about the same amount. "echo 3 > /proc/sys/vm/drop_caches" brings back the initial performance (~4s), but so do writing 1 or 2. This was reported almost two years ago in https://bugs.debian.org/702477 but I don't know if this is a known issue upstream. Seen on various kernel versions, up to 3.18. Is there anything we can do to track this down, or are there known workarounds for this? Thanks, Julien -- Julien Cristau Logilab http://www.logilab.fr/ Informatique scientifique & gestion de connaissances