Re: [PATCH] Performance Stats: Kernel patch

On Thu, 10 May 2007 11:11:18 +0000 Maxim Uvarov [off-list ref] wrote:

quoted

syscall entry is a super-hotpath and there will be a developer revolt
if we go adding an incl to that path, sorry.

 

Yes, I know that it is very critical part of code. May be protection with
ifdef CONFIG_TASKSTATS  in all entry.S can be solution?
In that case we can be sure that nothing wrong can not happen,
and if this functionality is needed we can turn on this.

I very much hope that all distributors will enable taskstats, so that won't
help.

I don't think the syscall-counting feature has a future, sorry.  Perhaps
you could do something like hooking it up on-demand by insertion of a kprobe,
dunno.

quoted

(Did that incl also cover the int 80 entry?)
 

Actually not. But counter increments each time when syscall  calls.
But it is in very save place, just after
        SAVE_ALL
        GET_THREAD_INFO(%ebp)
So it is very hard to break something.

What I meant was: the code appears to be counting sysenter-invoked syscalls,
but it isn't counting not int 80-invoked syscalls.