On 05/07/2015 08:29 AM, Ingo Molnar wrote: > > * Frederic Weisbecker <[email protected]> wrote: > >>>> We cannot take the lock_trace(task) from irq context, and we >>>> probably do not need to anyway, since we do not care about a >>>> precise stack trace for the task. >>> >>> So one worry with this and similar approaches of statistically >>> detecting user mode would be the fact that on the way out to >>> user-space we don't really destroy the previous call trace - we >>> just pop off the stack (non-destructively), restore RIPs and are >>> gone. >>> >>> We'll need that percpu flag I suspect. >> >> Note we have the context tracking state which tells where the >> current task is: user/system/guest. > > Yes, but that overhead is what I'm suggesting we get rid of, I thought > Rik was trying to find a mechanism that would be independent of that?
One thing at a time :) I am working on the timer sampling stuff, which should be easy to adapt to a different user/system/guest/irq/softirq/... tracking thing, if somebody else comes up with a more efficient way to do that. -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
