Messages in this thread | | | Date | Wed, 24 Sep 2008 17:08:33 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: [RFC PATCH 1/3] Unified trace buffer |
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On Wed, 24 Sep 2008, Martin Bligh wrote:
> > On Wed, 24 Sep 2008, Martin Bligh wrote: > >> > >> If we use 32 bits instead of 27, then the timestamp events are only > >> about once per second, which is probably fine for overhead ... ? > > > > You'd have them ONCE IN A BLUE MOON. > > > > If there is nothing going on, you don't need the timestamps at all. > > Yeah, you're right - we can just mark it dirty, and 'pre-log' the timestamp > events when someone calls a reserve and we haven't logged anything > for more time than we can store. Did not think of that. Was only 5 bits > for us, not an extra 37, but still, is much better. > > Is a 5-bit event id generic enough though? >
Actually, I was keeping the event id completely out of the ring buffer and let a higher layer deal with that. For padding, I just made the length field zero.
For overflows of the timestamp, we can reserve the -1 timestamp as a trigger to read the tsc again and put the full 64 bits into the record.
Just an idea.
-- Steve
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