Hi, On 21 September 2014 04:57, Akira Hayakawa <ruby.wktk@xxxxxxxxx> wrote: > I am writing a test with fio tool (2.0.8) and I am facing a problem. > > I just want to submit 512B random write to a block device. > In my case, the size of the device is 2MB and the amount of writes (specified by --size option) is 32MB. You probably wanted the behaviour of io_limit (http://git.kernel.dk/?p=fio.git;a=blob;f=HOWTO;h=73e58ff695c3384df30094d6c15ebe9ed615460f;hb=HEAD#l433 ) rather than size... > like this (A line from device-mapper-test-suite. Is my command wrong?): > ProcessControl.run("fio --name=test --filename=#{dev.path} --rw=randwrite --ioengine=libaio --direct=1 --size=#{@param[0]}m --bs=512") > > The problem is, the runtime is too short. > The block device is just a single HDD so, it will be 30sec or so. But it's actually 3sec... > > My guess is that fio uses min(device size, param to --size) as the amount of writes here. That's correct in this context - size is limiting the last possible block that can be written to (see http://git.kernel.dk/?p=fio.git;a=blob;f=HOWTO;h=73e58ff695c3384df30094d6c15ebe9ed615460f;hb=HEAD#l421 for details). > To investigate it, I increased the size of the device to x10 and saw the runtime gets x10. > > My questions are: > 1. Is my guess correct? Yes. > 2. What shall I do to make fio work as I want it to do? Use io_limit if your fio is new enough or number_ios (http://git.kernel.dk/?p=fio.git;a=blob;f=HOWTO;h=73e58ff695c3384df30094d6c15ebe9ed615460f;hb=HEAD#l778 ). Sitsofe | http://sucs.org/~sits/ -- 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
