From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sat, 10 Nov 2007 20:48:40 -0800 (PST) Received: from sandeen.net (sandeen.net [209.173.210.139]) by oss.sgi.com (8.12.11.20060308/8.12.10/SuSE Linux 0.7) with ESMTP id lAB4lu7o016633 for ; Sat, 10 Nov 2007 20:48:01 -0800 Message-ID: <4736897F.4070202@sandeen.net> Date: Sat, 10 Nov 2007 22:47:59 -0600 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: minor CPU wake-up question References: <47364104.8020106@tlinx.org> In-Reply-To: <47364104.8020106@tlinx.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Linda Walsh Cc: Linux-Xfs Linda Walsh wrote: > I recently ran into "powertop" (fr. lesswatts.org) that shows how often > interrupts awaken a processor under a tickless kernel. > > The display indicates the counts are over a 10 second period. > Barring any disk activity, why would xfsbufd wake up each copy of itself > up when there doesn't seem like there would be anything to do. > > Is a separate process really needed for each partition (that seems to be > the case)? I don't know if it is 1 interrupt/bufd or 6 on 1, but > it is fairly constant with 6 interrupts each period. > FWIW, dirty_writeback_centiseconds is set to 1500(1499) and makes > no difference in the count. > > It doesn't seem to be a big deal, other than it is at the top of the > interrupt-chart with usually 60% or more of the ticks. Might be nice > to not have it on top if it isn't necessary... I think by default, xfsbufd wakes up each second for each filesystem. See fs.xfs.xfsbufd_centisecs, default 100, or 1s. I think powertop is reporting wakeups/second, so it looks you have 6 filesystems mounted? Honestly if that's your most frequent entry, you're probably doing pretty well... -Eric