> Il giorno 16 ago 2019, alle ore 15:21, Josef Bacik <josef@xxxxxxxxxxxxxx> ha scritto: > > On Fri, Aug 16, 2019 at 12:57:41PM +0200, Paolo Valente wrote: >> Hi, >> I happened to test the io.latency controller, to make a comparison >> between this controller and BFQ. But io.latency seems not to work, >> i.e., not to reduce latency compared with what happens with no I/O >> control at all. Here is a summary of the results for one of the >> workloads I tested, on three different devices (latencies in ms): >> >> no I/O control io.latency BFQ >> NVMe SSD 1.9 1.9 0.07 >> SATA SSD 39 56 0.7 >> HDD 4500 4500 11 >> >> I have put all details on hardware, OS, scenarios and results in the >> attached pdf. For your convenience, I'm pasting the source file too. >> > > Do you have the fio jobs you use for this? The script mentioned in the draft (executed with the command line reported in the draft), executes one fio instance for the target process, and one fio instance for each interferer. I couldn't do with just one fio instance executing all jobs, because the weight parameter doesn't work in fio jobfiles for some reason, and because the ioprio class cannot be set for individual jobs. In particular, the script generates a job with the following parameters for the target process: ioengine=sync loops=10000 direct=0 readwrite=randread fdatasync=0 bs=4k thread=0 filename=/mnt/scsi_debug/largefile_interfered0 iodepth=1 numjobs=1 invalidate=1 and a job with the following parameters for each of the interferers, in case, e.g., of a workload made of reads: ioengine=sync direct=0 readwrite=read fdatasync=0 bs=4k filename=/mnt/scsi_debug/largefileX invalidate=1 Should you fail to reproduce this issue by creating groups, setting latencies and starting fio jobs manually, what if you try by just executing my script? Maybe this could help us spot the culprit more quickly. > I just tested on Jens's most recent > tree and io.latency appears to be doing what its supposed to be doing. We've > also started testing 5.2 in production and it's still working in production as > well. I tested 5.2 too, same negative outcome. Thanks, Paolo > The only thing I've touched recently was around wakeups and shouldn't > have broken everything. I'm not sure why it's not working for you, but a fio > script will help me narrow down what's going on. Thanks, > > Josef
