Subj : Re: Pointless waste of time
To   : comp.programming.threads
From : doug
Date : Thu Apr 21 2005 09:47 am


"Joe Seigh" <jseigh_01@xemaps.com> wrote in message 
news:opspg64xevqm36vk@grunion...
> On Tue, 19 Apr 2005 03:16:13 GMT, Randy Howard 
> <randyhoward@FOOverizonBAR.net> wrote:
>
>> In article <opspggduj1qm36vk@grunion>, jseigh_01@xemaps.com says...
>>> Just wasted the day testing various api's to see what they actually do.
>>> It would be nice if they started documenting what these api's did.
>>>
>>> Learned some interesting things about Linux /proc.  There's more there 
>>> than
>>> meets the eye.  Literally.  It's still totally useless compared to 
>>> Solaris
>>> or Aix, though.  Somebody take a cluebat to Linux kernel developers, 
>>> please.
>>
>> Care to enumerate the problems you encountered, or are we to guess?
>
> You mean was my post about as informative as some of the api man pages? :)
>
> If you want useless fun, try using any of the kernel thread ids for a 
> process,
> the stuff the task directory, as a process id.  E.g. if 5556 is in
> /proc/5555/task try "ls /proc/5556" even though you can't see a 
> /proc/5556.
>
> For an example of badly documented and/or somewhat useless api's, here's 
> one
> I didn't test yet.  I wasn't paying too much attention to the ITIMER 
> questions
> here at the time.  The claim is you can use ITIMER to profile processes. 
> But
> if signals go to only an enabled thread in a processes, not to all 
> threads, then
> you probably can't profile a multi-threaded process on a multi-processor 
> very
> well.  The documentation doesn't explicitly address this issue.  I'd have 
> to
> waste a bunch of time to confirm this one way or another.

You fix this by:

- in your main thread, getitimer(ITIMER_PROF, 
&address_of_some_global_struct_itimterval_variable);
- in the entry points of your other threads, setitimer(ITIMER_PROF, 
&address_of_some_global_struct_itimterval_variable);

This should enable profiling for all your threads.


>
> You have to check these things out because once in a while it turns out 
> some
> api will actually do something useful.  Yesterday it was one out of three.
>
>
>
> -- 
> Joe Seigh
>
> When you get lemons, you make lemonade.
> When you get hardware, you make software.

.