Hi Alexander On Wed, 27 May 2020 at 19:38, Alexander Monakov <amonakov@xxxxxxxxx> wrote: > > On Wed, 27 May 2020, Guenter Roeck wrote: > > > >> I understand that. If you anticipate that the module may be inserted after a > > >> wraparound, the driver should populate 'prev_value' with actual counter > > >> values instead of zeros. That way the driver will properly accumulate > > >> energy over time it's been inserted. As implemented, the driver counts > > >> energy since boot time, minus unknown amount lost to wraparounds if the > > >> driver was loaded too late. > > > No problem if this module is built into the kernel. > > > If this module is inserted at later point, unless the user keeps the > > > counters since > > > the boot and provide it as an input during the module insert (we can > > > implement this). > > > > I won't accept such a parameter. If you may recall, I did bring this up as > > reason why I abandoned the matching change for the coretemp driver, predicting > > that people would complain about it. Now they do. Not surprising. We (and you) > > will have to live with it. Yes agree, letting user provide initial values is not appropriate. My bad. > > I'm not exactly complaining, I'm proposing a solution: at probe time, populate > prev_value members with MSR values instead of zeros. That way, the module will > correctly count energy over the time it's been loaded. It can be unloaded and > reloaded freely, and doing so would allow to easily measure energy across large > spans of time, which sounds like an improvement. In the current driver, the accumulation thread starts during the probe and the prev_value of sockets and the core0 is updated with the current MSR value. It takes (nr_cpus - 1) iterations of the thread to populate the prev_value for the other cores. By populating prev_value of all the cores during probe, we can certainly save some information (values with in one wrap-around at the best). If this information is useful, i can submit a patch to do so. Guenter, could you suggest us on this. > > I can try to cook a corresponding patch if that sounds alright. > > Cheers. > Alexander -- Shine bright, (: Nav :)
