Messages in this thread | | | Date | Sat, 4 Oct 2008 09:20:00 +0200 | From | "stephane eranian" <> | Subject | Re: perfmon3 interface overview |
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David,
On Sat, Oct 4, 2008 at 8:05 AM, David Gibson <david@gibson.dropbear.id.au> wrote: >> >> If we wanted to go even further, we could combine start/stop, attach/detach >> into a single syscall: > > Well, you could. But the attach/detach take a parameter which > start/stop don't, making it a less obvious merge to make. > Unless you make the 3rd argument optional and hide this in a user library. This is how this is handled for pfm_create_session() for instance. The library would define this as follows:
int pfm_control_session(int fd, int flags, ...);
Based upon flags, it would use va_arg() to get to the 3rd argument and pass it to the syscall which implements the version below. A dummy value would be passed with the flags is not equal to PFM_CTFL_ATTACH.
>> int pfm_control_session(int fd, int flags, int target); >> With flags: >> PFM_CTFL_START : start monitoring >> PFM_CTFL_STOP : stop monitoring >> PFM_CTFL_RESTART: resume after overflow notification >> >> PFM_CTFL_ATTACH: attach to thread or cpu designated by 'target' >> PFM_CTFL_DETACH: detach session >>
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