Re: DTrace syscall provider - please test/comment

[christos%zoulas.com@localhost (Christos Zoulas)]

On Jun 25,  9:32am, matt%3am-software.com@localhost (Matt Thomas) wrote:
-- Subject: Re: DTrace syscall provider - please test/comment

| 
| On Jun 25, 2013, at 5:25 AM, christos%zoulas.com@localhost (Christos Zoulas) 
wrote:
| 
| > On Jun 24,  6:12pm, matt%3am-software.com@localhost (Matt Thomas) wrote:
| > -- Subject: Re: DTrace syscall provider - please test/comment
| > 
| > | 
| > | On Jun 24, 2013, at 6:01 PM, Christos Zoulas 
<christos%astron.com@localhost> wrote:
| > | 
| > | > Can't this be done as an addition/enhancement to the trace_enter()/
| > | > trace_exit() facility instead of having to enter each syscall entry?
| > | 
| > | that only gets called if p->p_trace_enabled is set.  So now you need
| > | a hook to set that on every lwp switch if the provider is tracing.
| > 
| > Right, and it (dtrace) can set a different (or the same flag) to enable
| > it.
| 
| 
| How does it set the same flag since that's per-proc and will need to changed
| on context switch.  
| 
| A different flag is more overhead per syscall.

I am trying to balance that against adding of two more conditionals per
syscall per architecture and touching dozens of source files adding the
same code in each one. Perhaps the syscall_plain/syscall_fancy idea
was not that bad after all :-( Perhaps a different bit on the same flag.
If any of them is set, you call trace enter, and you clear/move the
bit on context switch.

christos