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| -rw-r--r-- | share/man/man9/MUTEX_PROFILING.9 | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/share/man/man9/MUTEX_PROFILING.9 b/share/man/man9/MUTEX_PROFILING.9 index bbca8ab..7f8baf2 100644 --- a/share/man/man9/MUTEX_PROFILING.9 +++ b/share/man/man9/MUTEX_PROFILING.9 @@ -1,5 +1,6 @@ .\"- .\" Copyright (c) 2004 Dag-Erling Coïdan Smørgrav +.\" Copyright (c) 2005 Robert N. M. Watson .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without @@ -158,6 +159,12 @@ option also prevents inlining of the mutex code, which results in a fairly severe performance penalty. It should therefore only be enabled on systems where mutex profiling is actually needed. +.Dv MUTEX_PROFILING +will introduce a substantial performance overhead that is easily +monitorable using other profiling tools, so combining profiling tools +with +.Dv MUTEX_PROFILING +is not recommended. .Pp Measurements are made and stored in nanoseconds using .Xr nanotime 9 , @@ -165,3 +172,19 @@ but are presented in microseconds. This should still be sufficient for the locks one would be most interested in profiling (those that are held long and/or acquired often). +.Pp +.Dv MUTEX_PROFILING +should generally not be used in combination with other debugging options, as +the results may be strongly affected by interactions between the features. +In particular, +.Dv MUTEX_PROFILING +will report higher than normal +.Xr uma 9 +lock contention when run with +.Dv INVARIANTS +due to extra locking that occurs when +.Dv INVARIANTS +is present; likewise, using it in combination with +.Dv WITNESS +with +will lead to much higher lock hold times and contention in profiling output. |
