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 > Defines how files to service are selected. The follow‐ > ing types are defined: > > random Choose a file at random > > roundrobin > Round robin over open files (default). > sequential Do each file in the set sequen‐ > tially. > > The number of I/Os to issue before switching a new file > can be specified by appending `:int' to the service > type. > > ? (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! ;) > > Ciao, > -- > Martin 'Helios' Steigerwald - http://www.Lichtvoll.de > GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 > 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. Thanks, Greg. -- 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
