From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rolf Fokkens Subject: Re: bcache_writebac task 100% CPU Date: Mon, 19 May 2014 20:01:46 +0200 Message-ID: <537A470A.7080808@rolffokkens.nl> References: <53786E02.8060300@rolffokkens.nl> <20140519165550.GD2276@kmo> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ee0-f43.google.com ([74.125.83.43]:64253 "EHLO mail-ee0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbaESSBt (ORCPT ); Mon, 19 May 2014 14:01:49 -0400 Received: by mail-ee0-f43.google.com with SMTP id d17so3895958eek.30 for ; Mon, 19 May 2014 11:01:47 -0700 (PDT) In-Reply-To: <20140519165550.GD2276@kmo> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Kent Overstreet Cc: linux-bcache@vger.kernel.org On 05/19/2014 06:55 PM, Kent Overstreet wrote: > ...Changing it back to 25% doesn't do anything? _that_ is odd... I was wrong on this one. At first the CPU usage stayed the same, but after a while (as in > 10 minutes) CPU usage dropped to normal behaviour. Sorry, I was too impatient. > Can you send me the output of writeback_rate_debug? Check it once before you've > done anything, when things are working normally (after a fresh boot when > writeback_percent is nonzero, probably), then grab it again after you've set > writeback_percent to 0 and then back to 25, when it's still spinning. I will do so, probably tomorrow. > There seems to be two separate bugs here, the one I'm particularly concerned > about is why setting writeback_percent back to 25 doesn't restore the old > behaviour. > > Also, what kernel are you running? I am using Fedora kernel version kernel-3.14.4-200.fc20.x86_64