Re: [PATCH 1/2] Add trace points to mmap, munmap, and brk

[Ingo Molnar <mingo@elte.hu>]

* Eric B Munson <emunson@mgebm.net> wrote:

> Sorry for the long delay, the enter/exit routines are not compatible 
> with the information that these new trace points provides.  When 
> tracing mmap, for instance, the addr and len arguments can be altered 
> by the function.  If you use the enter/exit trace points you would not 
> see this as the arguments are sampled at function entrance and not 
> given again on exit.  Also, the new trace points are only hit on 
> function success, the exit trace point happens any time you leave the 
> system call.

Would it be feasible to use enter/exit information as the main source of 
events - and only add new tracepoints for the _missing_ information? 
(such as when mmap arguments change)

Then user-space can combine the two. The new tracepoints would also 
carry useful information in themselves: they would show the cases where 
user-space did not get what it wished. (or so)

Thanks,

	Ingo