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| author | Alan D. Brunelle <alan.brunelle@hp.com> | 2010-09-16 09:26:22 -0400 |
|---|---|---|
| committer | Alan D. Brunelle <alan.brunelle@hp.com> | 2010-09-16 09:26:22 -0400 |
| commit | ce2151ebdca6f2741dbd903aa3845c56adcba8f4 (patch) | |
| tree | 4c69b8f9136a8d709d535aff93567b876e5e59b7 /doc | |
| parent | fb7f86674a516ddff0d60bfab3bd284a4812075f (diff) | |
| download | blktrace-ce2151ebdca6f2741dbd903aa3845c56adcba8f4.tar.gz blktrace-ce2151ebdca6f2741dbd903aa3845c56adcba8f4.tar.bz2 | |
blktrace: disallow -o when using multiple devices
Document that "-o" does not work when specyfing multiple devices to
blktrace, also: enforce this by stopping blktrace when one tries do
do this.
The technical reason why "-o" doesn't work with multiple devices is
because we use multiple threads of execution - one per device/CPU pair -
and each of them opens a file named "<prefix>.blktrace.<cpu>". With the
"-o" all of the "<prefix>" values are the same - so multiple threads
open the same file and try to do output. Not good. Without the "-o"
we get unique files named: "<device>.blktrace.<cpu>" - as the tuple
(<device>,<cpu>) is unique.
Signed-off-by: Alan D. Brunelle <Alan.Brunelle@hp.com>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/blktrace.8 | 3 | ||||
| -rw-r--r-- | doc/blktrace.tex | 5 |
2 files changed, 7 insertions, 1 deletions
diff --git a/doc/blktrace.8 b/doc/blktrace.8 index ab6a3f3..50b3a62 100644 --- a/doc/blktrace.8 +++ b/doc/blktrace.8 @@ -122,6 +122,9 @@ Specifies number of buffers to use. blktrace defaults to 4 sub buffers. \-\-output=\fIfile\fR .RS Prepend \fIfile\fR to output file name(s) + +This only works when supplying a single device, or when piping the output +via "-o -" with multiple devices. .RE \-r \fIrel-path\fR diff --git a/doc/blktrace.tex b/doc/blktrace.tex index 54fe451..4d8278e 100644 --- a/doc/blktrace.tex +++ b/doc/blktrace.tex @@ -389,7 +389,10 @@ Short & Long & Description \\ \hline\hline -d \emph{dev} & --dev=\emph{dev} & Adds \emph{dev} as a device to trace \\ \hline -k & --kill & Kill on-going trace \\ \hline -n \emph{num-sub} & --num-sub=\emph{num-sub} & Specifies number of buffers to use \\ \hline --o \emph{file} & --output=\emph{file} & Prepend \emph{file} to output file name(s) \\ \hline +-o \emph{file} & --output=\emph{file} & Prepend \emph{file} to output file name(s) \\ + & & \textbf{This only works when using a single device} \\ + & & \textbf{or when piping the output via \texttt{-o -}} \\ + & & \textbf{with multiple devices.} \\ \hline -r \emph{rel-path} & --relay=\emph{rel-path} & Specifies debugfs mount point \\ \hline -V & --version & Outputs version \\ \hline -w \emph{seconds} & --stopwatch=\emph{seconds} & Sets run time to the number of seconds specified \\ \hline |