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1 .\" $NetBSD: 4.t,v 1.2 1998/01/09 06:41:23 perry Exp $
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3 .\" Copyright (c) 1984 The Regents of the University of California.
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30 .\" Copyright (c) 1984 M. K. McKusick
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54 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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60 .\" @(#)4.t 1.2 (Berkeley) 11/8/90
61 .\"
62 .ds RH Conclusions
63 .NH 1
64 Conclusions
65 .PP
66 We have created a profiler that aids in the evaluation
67 of the kernel.
68 For each routine in the kernel,
69 the profile shows the extent to which that routine
70 helps support various abstractions,
71 and how that routine uses other abstractions.
72 The profile assesses the cost of routines
73 at all levels of the kernel decomposition.
74 The profiler is easily used,
75 and can be compiled into the kernel.
76 It adds only five to thirty percent execution overhead to the kernel
77 being profiled,
78 produces no additional output while the kernel is running
79 and allows the kernel to be measured in its real environment.
80 Kernel profiles can be used to identify bottlenecks in performance.
81 We have shown how to improve performance
82 by caching recently calculated name translations.
83 The combined caches added to the name translation process
84 reduce the average cost of translating a pathname to an inode by 35%.
85 These changes reduce the percentage of time spent running
86 in the system by nearly 9%.
87 .nr H2 1
88 .ds RH Acknowledgements
89 .SH
90 \s+2Acknowledgements\s0
91 .PP
92 I would like to thank Robert Elz for sharing his ideas and
93 his code for cacheing system wide names.
94 Thanks also to all the users at Berkeley who provided all the
95 input to generate the kernel profiles.
96 This work was supported by
97 the Defense Advance Research Projects Agency (DoD) under
98 Arpa Order No. 4031 monitored by Naval Electronic System Command under
99 Contract No. N00039-82-C-0235.
100 .ds RH References
101 .nr H2 1
102 .sp 2
103 .SH
104 \s+2References\s-2
105 .LP
106 .IP [Bentley81] 20
107 Bentley, J. L.,
108 ``Writing Efficient Code'',
109 Department of Computer Science,
110 Carnegie-Mellon University,
111 Pittsburgh, Pennsylvania,
112 CMU-CS-81-116, 1981.
113 .IP [Graham82] 20
114 Graham, S., Kessler, P., McKusick, M.,
115 ``gprof: A Call Graph Execution Profiler'',
116 Proceedings of the SIGPLAN '82 Symposium on Compiler Construction,
117 Volume 17, Number 6, June 1982. pp 120-126
118 .IP [Graham83] 20
119 Graham, S., Kessler, P., McKusick, M.,
120 ``An Execution Profiler for Modular Programs''
121 Software - Practice and Experience,
122 Volume 13, 1983. pp 671-685
123 .IP [Ritchie74] 20
124 Ritchie, D. M. and Thompson, K.,
125 ``The UNIX Time-Sharing System'',
126 CACM 17, 7. July 1974. pp 365-375