Hi Sean - No, a quick way to identify an IO bottleneck does not exist, precisely because of all the layers in the IO stack.
First, describe the performance problem in measureable terms (time, amount of data, directory spread, file count, etc), including whether or not the problem is untar'ing a tar file (thus potentially doing a lot of file and directory creates), or creating a tar file (thus reading from a potentially wide and/or deep directory), or both. There are several ways to approach the problem, either through measurement and instrumentation, or process of elimination, or both. For the latter, it's often quick and easy to try the same operation on another file system on a different set of disks, or even a different system, just to sanity check your numbers. A simple "truss -c tar blah-blah-blah" to get a system call profile will often point you in the right direction, along with an "iostat -xz 1" in another terminal window while the tar is happening to determine how well (or poorly) the underlying disks are doing, keeping in mind that depending on a wide variety of things, the operation could be hitting files in the file system page cache (thus not resulting in physical disk IOs). For a problem like this, the first set of data will determine where you need to go to collect the next set of data (actually, pretty much all performance problems are like this! :^), which will likely be instrumenting with DTrace to chase it further. No silver bullet here - just a methodical set of steps, facilitated by an operating system with the richest set of tools for doing such things on the planet earth! Good luck - if you have data to share, please post it to the alias and we will try to help further (but please don't send me a 10MB tarball with the subject line "what's wrong" ;^)....you'd be surprised...). Thanks, /jim Sean Liu wrote: > Hi there, > > I am seeing a weird performance issue, tar command runs slow on top of a > filesyste. > I am wondering if there is a quick way to identify the bottleneck on the > whole IO path, i.e command -> FS module -> Volume management -> Multipatch -> > sd > > Any help is appreciated. > > Sean > > > This message posted from opensolaris.org > _______________________________________________ > perf-discuss mailing list > perf-discuss@opensolaris.org > _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
