From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from detritus.pyropus.ca ([64.5.53.58]:52860 "HELO detritus.pyropus.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751692AbaLYDL0 (ORCPT ); Wed, 24 Dec 2014 22:11:26 -0500 Date: Wed, 24 Dec 2014 21:15:45 -0600 From: Charles Cazabon To: btrfs list Subject: Re: Oddly slow read performance with near-full largish FS Message-ID: <20141225031545.GB5864@pyropus.ca> References: <20141217024228.GA5544@pyropus.ca> <54955624.5040808@pobox.com> <20141221163207.GA18988@pyropus.ca> <54973C65.6070709@pobox.com> <20141221225315.GA19479@pyropus.ca> <549827C3.6060009@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <549827C3.6060009@gmail.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Austin S Hemmelgarn wrote: > > This actually sounds kind of like the issues I have sometimes on my > laptop using btrfs on an SSD, I've mostly resolved them by tuning IO > scheduler parameters, as the default IO scheduler (the supposedly > Completely Fair Queue, which was obviously named by a mathematician > who had never actually run the algorithm) has some pretty brain-dead > default settings. The other thing I would suggest looking into > regarding the variability is tuning the kernel's write-caching > settings Ok, that's something I will examine. I knew CFQ is completely wrong for SSD use, but I thought it was still one of the better schedulers for spinning disks. Apparently that may not be the case. Thanks, Charles -- ----------------------------------------------------------------------- Charles Cazabon GPL'ed software available at: http://pyropus.ca/software/ -----------------------------------------------------------------------