From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brett Russ Date: Thu, 16 Sep 2010 14:20:51 +0000 Subject: Re: [PATCH] blktrace: disallow -o when using multiple devices Message-Id: <4C9227C3.7000404@netezza.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-btrace@vger.kernel.org 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 ".blktrace.". With the > "-o" all of the"" 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: ".blktrace." - as the tuple > (,) is unique. Alan, -Wouldn't it be a good idea to just add 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 "..blktrace."? 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