From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sat, 10 Nov 2007 16:00:18 -0800 (PST) Received: from ishtar.tlinx.org (ishtar.tlinx.org [64.81.245.74]) by oss.sgi.com (8.12.11.20060308/8.12.10/SuSE Linux 0.7) with ESMTP id lAB00Abr019076 for ; Sat, 10 Nov 2007 16:00:12 -0800 Received: from [192.168.3.11] (Athena [192.168.3.11]) by ishtar.tlinx.org (8.13.3/8.12.10/SuSE Linux 0.7) with ESMTP id lAANciJe013460 for ; Sat, 10 Nov 2007 15:38:44 -0800 Message-ID: <47364104.8020106@tlinx.org> Date: Sat, 10 Nov 2007 15:38:44 -0800 From: Linda Walsh MIME-Version: 1.0 Subject: minor CPU wake-up question Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Linux-Xfs 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... 63.2% ( 6.0) xfsbufd : schedule_timeout (process_timeout) 21.1% ( 2.0) : clocksource_register (clocksource_watchdog) 2.1% ( 0.2) : __netdev_watchdog_up (dev_watchdog) 2.1% ( 0.2) : page_writeback_init (wb_timer_fn) 2.1% ( 0.2) : neigh_table_init_no_netlink (neigh_periodic_ 2.1% ( 0.2) init : schedule_timeout (process_timeout) 1.1% ( 0.1) xfssyncd : schedule_timeout (process_timeout) 1.1% ( 0.1) : init_nonfatal_mce_checker (delayed_work_time 1.1% ( 0.1) cron : do_nanosleep (hrtimer_wakeup) 1.1% ( 0.1) nscd : schedule_timeout (process_timeout) 1.1% ( 0.1) irqbalance : do_nanosleep (hrtimer_wakeup) 1.1% ( 0.1) : __neigh_event_send (neigh_timer_handler) 1.1% ( 0.1) : dst_run_gc (dst_run_gc) ----