on 2/9/2024 3:32 AM, Tejun Heo wrote: > Hello, Kemeng. > > On Thu, Feb 08, 2024 at 05:26:10PM +0800, Kemeng Shi wrote: >> Hi Tejun, sorry for the delay as I found there is a issue that keep triggering >> writeback even the dirty page is under dirty background threshold. The issue >> make it difficult to observe the expected improvment from this patch. I try to >> fix it in [1] and test this patch based on the fix patches. >> Run test as following: > > Ah, that looks promising and thanks a lot for looking into this. It's great > to have someone actually poring over the code and behavior. Understanding > the wb and cgroup wb behaviors have always been challenging because the only > thing we have is the tracepoints and it's really tedious and difficult to > build an overall understanding from the trace outputs. Can I persuade you > into writing a drgn monitoring script similar to e.g. > tools/workqueues/wq_monitor.py? I think there's a pretty good chance the > visibility can be improved substantially. Hi Tejun, sorry for the late reply as I was on vacation these days. I agree that visibility is poor so I have to add some printks to debug. Actually, I have added per wb stats to improve the visibility as we only have per bdi stats (/sys/kernel/debug/bdi/xxx:x/stats) now. And I plan to submit it in a new series. I'd like to add a script to improve visibility more but I can't ensure the time to do it. I would submit the monitoring script with the per wb stats if the time problem does not bother you. Thanks. > > Thanks. >
