On 08/30/2013 10:03 AM, Steven Rostedt wrote: > On Fri, 30 Aug 2013 09:35:18 -0700 > "H. Peter Anvin" <h...@zytor.com> wrote: > >> On 08/30/2013 08:51 AM, Steven Rostedt wrote: >>> >>> It does when dynamic tracing is enabled. But this issue is with static >>> tracing, there's no code modification, thus all functions call >>> mcount/__fentry__ and we need to look at a variable to determine if we >>> should trace or not. >>> >> >> And of course global variables are a no-no without special handling in >> pre-paging mode. Sigh. >> >> You *could* bail out of the calling address is < PAGE_OFFSET. >> > > We could do that too, as static tracing already gives us high overhead, > I'm not sure how much more overhead another check like this even > matters.
It's not too expensive: a compare and a jump. > Who uses static tracing? I only use it to test that it still works ;-) Can we get rid of it? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
