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Document the PMC_F_CALLCHAIN flag and the kern.hwpmc.callchaindepth

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tunable.

Sponsored by:	FreeBSD Foundation and Google Inc.
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Joseph Koshy 2007-12-07 08:29:46 +00:00
parent b6010f9e61
commit a07d350c16
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23
share/man/man4/hwpmc.4
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@ -1,6 +1,10 @@
.\" Copyright (c) 2003-2007 Joseph Koshy
.\" Copyright (c) 2007 The FreeBSD Foundation
.\" All rights reserved.
.\"
.\" Portions of this software were developed by A. Joseph Koshy under
.\" sponsorship from the FreeBSD Foundation and Google, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
@ -76,10 +80,11 @@ system call on all architectures.
Some architectures offer faster methods of reading these counts.
.It Em Sampling
In sampling modes, the PMCs are configured to sample the CPU
instruction pointer after a configurable number of hardware events
have been observed.
These instruction pointer samples are usually directed to a log file
for subsequent analysis.
instruction pointer (and optionally to capture the call chain leading
upto the sampled instruction pointer) after a configurable number of
hardware events have been observed.
Instruction pointer samples and call chain records are usually
directed to a log file for subsequent analysis.
.El
.Pp
Scope and operational mode are orthogonal; a PMC may thus be
@ -181,6 +186,13 @@ The
operation supports the following flags that modify the behavior
of an allocated PMC:
.Bl -tag -width indent
.It Dv PMC_F_CALLCHAIN
This modifier informs sampling PMCs to record a callchain when
capturing a sample.
The maximum depth to which call chains are recorded is specified
by the
.Va "kern.hwpmc.callchaindepth"
kernel tunable.
.It Dv PMC_F_DESCENDANTS
This modifier is valid only for a PMC being allocated in process-private
mode.
@ -391,6 +403,9 @@ and
.Xr loader 8
tunables:
.Bl -tag -width indent
.It Va kern.hwpmc.callchaindepth Pq integer, read-only
The maximum number of call chain records to capture per sample.
The default is 8.
.It Va kern.hwpmc.debugflags Pq string, read-write
(Only available if the
.Nm