Am Dienstag, 14. August 2012 schrieb Greg Sullivan: > On 15/08/2012, Martin Steigerwald <Martin@xxxxxxxxxxxx> wrote: > > Am Dienstag, 14. August 2012 schrieb Greg Sullivan: > >> On 15 August 2012 03:36, Martin Steigerwald <Martin@xxxxxxxxxxxx> wrote: > >> > Hi Greg, > > […] > >> > Am Dienstag, 14. August 2012 schrieb Greg Sullivan: > >> > > >> >> On Aug 14, 2012 11:06 PM, "Jens Axboe" <axboe@xxxxxxxxx> wrote: > >> >> > > >> >> > On 08/14/2012 08:24 AM, Greg Sullivan wrote: > >> >> > > I need to simulate strict synchronous, round robin i/o to a group > >> >> > > of > >> >> > > files. I am on Windows 7 32-bit. > >> >> > > fio is very nearly working, except that even with a queue depth of > >> >> > > 1, > >> >> > > it is still resulting in a disk queue that is > 1, because the > >> >> > > "iodepth" parameter is not global - it is per thread. (correct?) > >> >> > > > >> >> > > I've tried using the "sync" engine, however that doesn't work at > >> >> > > all - > >> >> > > just spews out errors. > >> >> > > >> >> > That'll be the case for ANY platform and IO engine. If you have more > >> >> > than 1 thread or process going, you can have > 1 depth at the device > >> >> > side. The definition of a sync IO call is that the call doesn't > >> >> > return > >> >> > until the IO is done. If you have overlapped calls due to more than > >> >> > 1 > >> >> > thread, then that is no longer true. > >> >> > > >> >> > What you are looking for is outside the scope of an application. You > >> >> > would have to limit the queue depth on the operating system side to > >> >> > achieve that. Or artificially limit fio in some way, which would not > >> >> > make a lot of sense imho. > >> > > >> >> Thanks Jens. I do in fact have an application that reads in exactly > >> >> the > >> >> manner I described. I have monitored the queue depth - it does not > >> >> rise > >> >> above 1. It is a real time musical sample streamer. > >> >> > >> >> Please consider this a new feature request for fio - thankyou. > >> > > >> > Is this application multithreaded? If so, are mutiple threads doing I/O > >> > at the same time? If not I´d suggest just testing with one job. > >> > >> I don't know whether it is multithreaded or not. All I know is that it > >> reads many files sequentially and in a round-robin fashion, without > >> causing any disk queuing. > >> > >> Is it possible to read from more than file in a single job, in a > >> round-robin fashion? I tried putting more than one file in a single > >> job, but it only opened one file. If you mean to just do random reads > >> in a single file - I've tried that, and the throughput is > >> unrealistically low. I suspect it's because the read-ahead buffer > >> cannot be effective for random accesses. Of course, reading > >> sequentially from a single file will result in a throughput that is > >> far too high to simulate the application. > > > > Have you tried > > > > nrfiles=int > > Number of files to use for this job. Default: 1. > > > > openfiles=int > > Number of files to keep open at the same time. Default: > > nrfiles. > > > > file_service_type=str […] > > ? (see fio manpage). > > > > It seems to me that all you need is nrfiles. I´d bet that fio distributes > > the I/O size given among those files, but AFAIR there is something about > > that in fio documentation as well. > > > > Use the doc! ;) […] > Yes, I have tried all that, and it works, except that it causes disk > queuing, as I stated in my first post. I thought you meant to put all > the files into a single [job name] section of the ini file, to enforce > single threaded io. With just one job running at once? Can you post an example job file? Did you try the sync=1 / direct=1 suggestion from Bruce Chan? I only know the behaviour of fio on Linux where I/O depth of greater than one is only possible with libaio and direct=1. The manpage hints at I/O depth is one for all synchronous I/O engines, so I´d bet that refers to Windows as well. Other than that I have no idea. -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
