Currently "start" starts the timers in all CPUs, and start profling. Stop does the contrary. Profile data is no more "volatile" and you can use "cp" instead of baing forced to use "cat", which was kind of weird. The cost of profiling is not only RAM. With hooks now in MM and process creation, there is a little cost there as well.
On Thu, Nov 5, 2015 at 11:07 AM, Barret Rhoden <[email protected]> wrote: > On 2015-10-31 at 10:06 "'Davide Libenzi' via Akaros" > <[email protected]> wrote: > > Moreover, I think the kprofinit is called at boot time, which > > allocates and sets up the profiler, even though nobody is using it. > > IMO the profiler should have zero cost if nobody is using it, and the > > setup should be done once the first user attaches, and be undone > > after the last detaches. > > One thing is that the only cost to kprofinit() is RAM. Tracking the > attach/detach is a bit more painful, but if you want to do it, then go > for it. It'll also require being more careful about removing the > per-cpu buffers (need to make sure there are no samples in progress > across the entire machine in a race-free manner). You also need to > know when the last user detaches (there is no 'detach' command). The > hassle didn't seem worth the RAM. > > Another alternative would be to only do the init stuff the first time > attach is called (use the run_once() macro). That way the RAM usage of > init() is only taken on attach, but we don't need to deal with removing > it. > > As far as other cleanup goes, there's other stuff in there that might > be deletable. Anything related to Kprofdataqid can probably be > removed. That's the old sampling profiler from Plan 9, and I don't > imagine we'll be using it again. (Let me know if I'm wrong, Ron.) > > Barret > > -- > You received this message because you are subscribed to the Google Groups > "Akaros" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Akaros" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. For more options, visit https://groups.google.com/d/optout.
