On 09/16/2010 08:33 AM, Alan D. Brunelle wrote:
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.
Alan,
-Wouldn't it be a good idea to just add <prefix> before the filename(s)
that would have been created in either the single or multiple device
case? I.e. in the multiple device case, how about
"<prefix>.<device>.blktrace.<cpu>"? That way the program always does
what the user wants, no special case documentation required.
-I just tested that the blktrace "-D" option (output dir, create if
doesn't exist) works for the multiple device case as long as the -o
option isn't also used. So, this is another alternative.
-I found the following inconsistencies between the doc and the command
line help, these would probably be a separate patch:
--blktrace
---doc is missing -[Dhlps]
---doc still contains deprecated option -k
--blkparse
---doc is missing -[aAD]
---doc still contains deprecated option -m
Thanks,
Brett
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