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Message-ID: <48354470.60403@miraclelinux.com> Date: Thu, 22 May 2008 19:01:20 +0900 From: Hirofumi Nakagawa <hnakagawa@...aclelinux.com> To: linux-kernel@...r.kernel.org CC: akpm@...ux-foundation.org, Andi Kleen <andi@...stfloor.org> Subject: [RFC][PATCH 1/2 v2] MAZE: Documentation/maze.txt Signed-off-by: Hirofumi Nakagawa <hnakagawa@...aclelinux.com> --- Documentation/maze.txt | 103 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6.26-rc2-mm1/Documentation/maze.txt 2008-05-22 10:23:10.000000000 +0900 @@ -0,0 +1,103 @@ + MAZE + ---- +Written by Hirofumi Nakagawa <hnakagawa@...aclelinux.com> based +on Documentation/cpusets.txt and Documentation/cgroups.txt + +Original copyright statements from cpusets.txt: +Portions Copyright (C) 2004 BULL SA. +Portions Copyright (c) 2004-2006 Silicon Graphics, Inc. + +CONTENTS: +========= + +1. MAZE + 1.1 What is MAZE ? + 1.2 Why is MAZE needed ? + 1.3 What is the difference between MAZE and rlimit ? +2. Usage Examples + 2.1 Adding watch task + 2.2 Getting watch task list + +1. MAZE +================= + +1.1 What is MAZE ? +---------------------- + +MAZE provides a mechanism for detecting excessive CPU cycle usage of +selected processes and sending signals to them. + +The definition of excessive CPU cycle usage is staying in TASK_RUNNINT +state for a long time. +Normally, a working process doesn't stay long time in TASK_RUNNING state +because of occasional IO waits or calling sleeps. +MAZE detects excessive CPU cycle usage from process's information and sends +signal when time of staying in TASK_RUNNING exceeds user defined limits. + +The aim is to implement a CGL (Carrier Grade Linux) requirement (AVL.14.0). + +Quote +from CGL specification: +(http://developer.osdl.org/dev/cgl/cgl40/cgl40-availability.pdf) + +OSDL CGL specifies that carrier grade Linux shall provide a +mechanism that detects excessive CPU cycle usage by any process or thread. +To enable detection, the following capabilities shall be provided: + - Communication between the monitoring process and the kernel. + - Registering a list of processes or threads and their allowed CPU cycle + thresholds. + - Ability to define policy based on process events including process/thread + creation and exit. + - Ability to take action whenever an event occurs. + - Ability to set the CPU cycle threshold to a resolution of one millisecond. + + +1.2 Why is MAZE needed ? +---------------------- + +MAZE can improve availability of a system. +An unexpected excessive CPU cycle usage does affect the system. +It is serious, especially in systems with tight resouce such as embedded. +MAZE can detect such processes, kill or notify them. + +1.3 What is the difference between MAZE and rlimit(RLIMIT_CPU) ? +---------------------- + +The differences with MAZE and rlimit are as follows. + - MAZE detects excessive CPU cycle usage, but rlimits limits total amount + of CPU usage. + MAZE can safely handle CPU intensive but correctly running processes. + + - User processes can add watched processes in MAZE. + + - MAZE allows users to choose a way how to act on the process, + sending a selected signal. + +2. Usage Examples +================= + +2.1 Adding watch task +---------------------- + +Adding a task to watch. + +# echo "[PID] [Soft limit] [Hard limit] [Soft signal] [Hard signal]" > \ + /proc/maze/entries + +The numeric values are "pid","soft limit [msec]","hard limit [msec]", +"soft signal" and "hard signal". + +For example, + +# echo "2206 15000 30000 24 9" > /proc/maze/entries + +2.2 Getting watch task list. +---------------------- + +Getting registed task list. + +# cat /proc/maze/entries +pid:2209 count: 0 soft-limit:15000 hard-limit:30000 soft-signal: 24 hard-signal: 9 +pid:2207 count: 0 soft-limit:15000 hard-limit:30000 soft-signal: 24 hard-signal: 9 +pid:2206 count: 100 soft-limit:15000 hard-limit:30000 soft-signal: 24 hard-signal: 9 + -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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