From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755298AbXD0ElP (ORCPT ); Fri, 27 Apr 2007 00:41:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755299AbXD0ElP (ORCPT ); Fri, 27 Apr 2007 00:41:15 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:58564 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755298AbXD0ElO (ORCPT ); Fri, 27 Apr 2007 00:41:14 -0400 Date: Fri, 27 Apr 2007 13:39:14 +0900 Message-ID: <877irysa6l.wl%takeuchi_satoru@jp.fujitsu.com> From: Satoru Takeuchi To: Linux Kernel Cc: Thomas Gleixner , Ingo Molnar Subject: [PATCH] fix hrtimers documentation User-Agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (=?ISO-8859-4?Q?Shij=F2?=) APEL/10.6 Emacs/21.4 (i486-pc-linux-gnu) MULE/5.0 (SAKAKI) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Fix hrtimers documentation. - The word `patch' is used to indicate hrtimers subsystem implementation. However this subsystem has already been in ustream kernel, so convert them into appropriate phrases. - Some minor cleanups. Signed-off-by: Satoru Takeuchi Index: linux-2.6.21/Documentation/hrtimers/hrtimers.txt =================================================================== --- linux-2.6.21.orig/Documentation/hrtimers/hrtimers.txt 2007-04-27 12:45:56.000000000 +0900 +++ linux-2.6.21/Documentation/hrtimers/hrtimers.txt 2007-04-27 13:24:22.000000000 +0900 @@ -1,8 +1,9 @@ hrtimers - subsystem for high-resolution kernel timers ----------------------------------------------------- +------------------------------------------------------ -This patch introduces a new subsystem for high-resolution kernel timers. +This document describes hrtimers, a new subsystem for high-resolution +kernel timers. One might ask the question: we already have a timer subsystem (kernel/timers.c), why do we need two timer subsystems? After a lot of @@ -78,7 +79,7 @@ from 250 Hz to 100 HZ (or even smaller). hrtimer subsystem implementation details ---------------------------------------- -the basic design considerations were: +The basic design considerations were: - simplicity @@ -87,7 +88,7 @@ the basic design considerations were: - simplification of existing, timing related kernel code -another basic requirement was the immediate enqueueing and ordering of +Another basic requirement was the immediate enqueueing and ordering of timers at activation time. After looking at several possible solutions such as radix trees and hashes, we chose the red black tree as the basic data structure. Rbtrees are available as a library in the kernel and are @@ -138,23 +139,22 @@ details.) hrtimers - rounding of timer values ----------------------------------- -the hrtimer code will round timer events to lower-resolution clocks +The hrtimer code will round timer events to lower-resolution clocks because it has to. Otherwise it will do no artificial rounding at all. -one question is, what resolution value should be returned to the user by +One question is, what resolution value should be returned to the user by the clock_getres() interface. This will return whatever real resolution a given clock has - be it low-res, high-res, or artificially-low-res. hrtimers - testing and verification ----------------------------------- +----------------------------------- -We used the high-resolution clock subsystem ontop of hrtimers to verify +We used the high-resolution clock subsystem on top of hrtimers to verify the hrtimer implementation details in praxis, and we also ran the posix timer tests in order to ensure specification compliance. We also ran tests on low-resolution clocks. -The hrtimer patch converts the following kernel functionality to use -hrtimers: +hrtimers converts the following kernel functionality to use it: - nanosleep - itimers