> Il giorno 22 apr 2018, alle ore 15:29, jianchao.wang <jianchao.w.wang@xxxxxxxxxx> ha scritto: > > Hi Paolo > > I used to meet similar issue on io.low. > Can you try the following patch to see whether the issue could be fixed. > https://marc.info/?l=linux-block&m=152325456307423&w=2 > https://marc.info/?l=linux-block&m=152325457607425&w=2 > Just tried. Unfortunately, nothing seems to change :( Thanks, Paolo > Thanks > Jianchao > > On 04/22/2018 05:23 PM, Paolo Valente wrote: >> Hi Shaohua, all, >> at last, I started testing your io.low limit for blk-throttle. One of >> the things I'm interested in is how good throttling is in achieving a >> high throughput in the presence of realistic, variable workloads. >> >> However, I seem to have bumped into a totally different problem. The >> io.low parameter doesn't seem to guarantee what I understand it is meant >> to guarantee: minimum per-group bandwidths. For example, with >> - one group, the interfered, containing one process that does sequential >> reads with fio >> - io.low set to 100MB/s for the interfered >> - six other groups, the interferers, with each interferer containing one >> process doing sequential read with fio >> - io.low set to 10MB/s for each interferer >> - the workload executed on an SSD, with a 500MB/s of overall throughput >> the interfered gets only 75MB/s. >> >> In particular, the throughput of the interfered becomes lower and >> lower as the number of interferers is increased. So you can make it >> become even much lower than the 75MB/s in the example above. There >> seems to be no control on bandwidth. >> >> Am I doing something wrong? Or did I simply misunderstand the goal of >> io.low, and the only parameter for guaranteeing the desired bandwidth to >> a group is io.max (to be used indirectly, by limiting the bandwidth of >> the interferers)? >> >> If useful for you, you can reproduce the above test very quickly, by >> using the S suite [1] and typing: >> >> cd thr-lat-with-interference >> sudo ./thr-lat-with-interference.sh -b t -w 100000000 -W "10000000 10000000 10000000 10000000 10000000 10000000" -n 6 -T "read read read read read read" -R "0 0 0 0 0 0" >> >> Looking forward to your feedback, >> Paolo >> >> [1] >>
