fd4c2b74f3
The implementation is in libblockdriver, and works transparently for all block drivers. The new btrace(8) tool can be used to control block tracing; see ``man btrace'' for details.
60 lines
2.2 KiB
Groff
60 lines
2.2 KiB
Groff
.TH BTRACE 8
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.SH NAME
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btrace \- block-level tracing interface
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.SH SYNOPSIS
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\fBbtrace\fR \fBstart\fR \fIdevice\fR \fIentries\fR
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.PP
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\fBbtrace\fR \fBstop\fR \fIdevice\fR \fIfile\fR
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.PP
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\fBbtrace\fR \fBreset\fR \fIdevice\fR
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.PP
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\fBbtrace\fR \fBdump\fR \fIfile\fR
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.SH DESCRIPTION
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The \fBbtrace\fR tool is the user interface to MINIX3's block-level tracing
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facility. It allows one to start, stop, and reset tracing, and dump a trace
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output file in a somewhat human-readable format.
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.SH COMMANDS
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.TP 10
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\fBstart\fR
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This command starts tracing all block requests on the given \fIdevice\fR. Each
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block request takes up one entry in the log. The \fIentries\fR parameter
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specifies the allocation side of the log in the driver process, in number of
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(32-byte) entries. Once the log is full, no more entries will be added.
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.TP 10
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\fBstop\fR
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This command stops tracing on the given \fIdevice\fR, and dumps the resulting
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log to the given output \fIfile\fR.
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.TP 10
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\fBreset\fR
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This command stops tracing on the given \fIdevice\fR and resets the state of
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the block tracer. This should be useful only in emergency situations.
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.TP 10
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\fBdump\fR
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Dump the contents of a log file generated earlier with \fBbtrace stop\fR, in
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human-readable format. Heavy users of the block tracing facility will probably
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want to write their own tools for parsing and visualizing dump files.
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.SH LIMITATIONS
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Only one block device can be traced per driver at once. It is therefore also
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not possible to trace a device and all its partitions at the same time. The
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tracing facility has been designed for tracing activity of a single file
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system, in which case these limitations are not important.
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.PP
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The log will always start with a \fIclose\fR operation on the device, since
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\fBbtrace\fR closes the file descriptor used to instruct the driver to start
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tracing. Similarly, for logs that have not already filled up during tracing,
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the last entry will be a \fBbtrace\fR-triggered \fIopen\fR operation.
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.SH EXAMPLES
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.TP 35
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.B btrace start /dev/c2d0 10240
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# Start a block trace on c2d0.
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.TP 35
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.B btrace stop /dev/c2d0 outfile
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# Stop the block trace on c2d0.
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.TP 35
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.B btrace dump outfile
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# View the output of the trace.
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.SH "SEE ALSO"
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.BR ioctl (2).
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.SH AUTHOR
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David van Moolenbroek <david@minix3.org>
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