Messages in this thread | | | Date | Wed, 24 Sep 2008 15:41:06 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [RFC PATCH 1/3] Unified trace buffer |
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On Wed, 24 Sep 2008, Linus Torvalds wrote: > > - case 1: TSCExtend marker > data = extended TSC (bits 28..59) > size = 8 > > - case 2: TimeStamp marker > data = tv_nsec > array[0] = tv_sec > size = 16
Btw, in case it wasn't clear, those two are totally different things.
The "case 1" thing is the thing that gets inserted automatically by the trace code when it's needed because the 27-bit TSC is too limited.
The "case 2" thing is to allow us to occasionally synchronize with some global known wall-time clock like the HPET + xtime. IOW, it would be something that on demand creates a mapping from wall clock to TSC for that particular CPU.
I guess I should perhaps have put the TSC frequency in there in that "case 2" thing too. Maybe that should be in "data" (in kHz) and tv_sec/tv_nsec should be in array[0..1], and the time sync packet would be 24 bytes.
Linus
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