Hi Tejun Thanks so much your comment :) I really appreciate it. On 2022/1/14 1:01 上午, Tejun Heo wrote: > Hello, > > On Thu, Jan 13, 2022 at 10:40:27AM +0800, Wang Jianchao wrote: >> bw/iops/lat of data or metadata of one cgroup is very basic statistics > > bw and iops can already be derived from the cumulative counters in io.stat. > Latencies without distribution are often what we tradtionally exposed not > because they're great but because exposing distributions is so cumbersome > from kernel. Also, latency numbers at cgroup level isn't *that* useful > anyway. There isn't a lot you can deduce for the particular cgroup from that > number. I agree with this. But my customer would yell at me because they really want to see that.... > >> which kernel could provide especially when cgroup is employed everywhere. >> And we love to collect them all the time during the instance in cgroup is >> running. > > It's really not that difficult to collect these numbers from bpf with pretty > low overhead. There's the problem of deployment for which there isn't "the" > right and convenient way but it'd be more worthwhile to put efforts towards > that. > >>> What if I want to know what portions are random, or the >>> distribution of IO sizes? >> This looks really detailed statistics :) >>> Do I add another rq-qos policy or add another >>> interface file with interface versioning? >> This iostat module can not provide all the kinds of statistics we want >> but just some very basic things. And maybe it can provide better hooks >> to install the ebpf program to collect detailed statistics. > > I mean, "really basic" means different things for different folks. Bytes / > ios, we all seem to agree. Beyond that, who knows? There already are enough > hooks to collect stats that you're trying to collect. The examples in py-bcc > might be a good place to start. Thanks for your suggestion. I will read it and try with bpf Best Regards Jianchao
