Messages in this thread | | | Date | Thu, 07 May 2015 11:47:38 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH 3/3] context_tracking,x86: remove extraneous irq disable & enable from context tracking on syscall entry |
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On 05/07/2015 08:29 AM, Ingo Molnar wrote: > > * Frederic Weisbecker <fweisbec@gmail.com> 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
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