dtrace discuss - Oct 2005 - finding the correct return from mmap

Hi all,
I have a problem with a script I am running to determine how much  
time is spent in the syscall mmap for one particular file which is  
mapped in a large number of times.  The problem is I can not think of  
a way to identify the return of the particular mmap in question.

Here is the script.

#!/usr/sbin/dtrace -qs

BEGIN
{
         dts = timestamp;
}

syscall::mmap:entry
/execname == "ttcs" && arg4==38/
{
         self->ts=timestamp;
         @cnt["Num of mmaps"] = count();
}

#here is the problem how do I work out if it is the return of the  
mmap I am interested in?
syscall::mmap:return
/self->ts && execname == "ttcs"/
{
         @["total time in mmap"] = sum((timestamp - self->ts));
}

END
{
         printf("Total time spent in dtrace is %d \n", (timestamp -  
dts));
}


Regards
Damien

Damien,

in the mmap:return case, you need to reset self->ts to 0 (after using it
:-). That way, you can be sure that you''ll only catch mmap:return
clauses where mmap:entry has first taken place.


thus:

syscall::mmap:return
/self->ts/
{
	/* do your bit */
	self->ts = 0;
}


HTH

Damien Cooke wrote:
> 
> Hi all,
> I have a problem with a script I am running to determine how much
> time is spent in the syscall mmap for one particular file which is
> mapped in a large number of times.  The problem is I can not think of
> a way to identify the return of the particular mmap in question.
> 
> Here is the script.
> 
> #!/usr/sbin/dtrace -qs
> 
> BEGIN
> {
>          dts = timestamp;
> }
> 
> syscall::mmap:entry
> /execname == "ttcs" && arg4==38/
> {
>          self->ts=timestamp;
>          @cnt["Num of mmaps"] = count();
> }
> 
> #here is the problem how do I work out if it is the return of the
> mmap I am interested in?
> syscall::mmap:return
> /self->ts && execname == "ttcs"/
> {
>          @["total time in mmap"] = sum((timestamp -
self->ts));
> }
> 
> END
> {
>          printf("Total time spent in dtrace is %d \n", (timestamp
-
> dts));
> }
> 
> Regards
> Damien
> 
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org
-- 
Michael Schuster
Sun Microsystems