Hi Tejun and Joseph On 04/27/2018 02:32 AM, Tejun Heo wrote: > Hello, > > On Tue, Apr 24, 2018 at 02:12:51PM +0200, Paolo Valente wrote: >> +Tejun (I guess he might be interested in the results below) > > Our experiments didn't work out too well either. At this point, it > isn't clear whether io.low will ever leave experimental state. We're > trying to find a working solution. Would you please take a look at the following two patches. https://marc.info/?l=linux-block&m=152325456307423&w=2 https://marc.info/?l=linux-block&m=152325457607425&w=2 In addition, when I tested blk-throtl io.low on NVMe card, I always got even if the iops has been lower than io.low limit for a while, but the due to group is not idle, the downgrade always fails. tg->latency_target && tg->bio_cnt && tg->bad_bio_cnt * 5 < tg->bio_cn the latency always looks well even the sum of two groups's iops has reached the top. so I disable this check on my test, plus the 2 patches above, the io.low could basically works. My NVMe card's max bps is ~600M, and max iops is ~160k. Here is my config io.low riops=50000 wiops=50000 rbps=209715200 wbps=209715200 idle=200 latency=10 io.max riops=150000 There are two cgroups in my test, both of them have same config. In addition, saying "basically work" is due to the iops of the two cgroup will jump up and down. such as, I launched one fio test per cgroup, the iops will wave as following: group0 30k 50k 70k 60k 40k group1 120k 100k 80k 90k 110k however, if I launched two fio tests only in one cgroup, the iops of two test could stay about 70k~80k. Could help to explain this scenario ? Thanks in advance Jianchao
