Re: precompiled probing scenarios

[David Smith <dsmith@redhat.com>]

Frank Ch. Eigler wrote:
> Hi -
> 
> On Fri, Oct 20, 2006 at 02:26:32PM -0500, David Smith wrote:
>> [...]
>> Pass 4: compiled C into "stap_d833fd040735ddde57a23bebb4456542_201.ko" 
> 
> Is that "_201" at the end the getuid()?  I wonder if maybe that could
> be hashed into the content instead.

Nope, that is part of the hash.  It might be the number of input bits, 
I'm unsure.

I don't hash the getuid(), since:
- by default your cache is stored in your home directory
- who you are doesn't change the pass 2-4 output

>> Copying /tmp/stapYrsXWC/stap_d833fd040735ddde57a23bebb4456542_201.ko to 
>> /home/dsmith/.stap_cache/d/8/stap_d833fd040735ddde57a23bebb4456542_201.ko
>> Copying /tmp/stapYrsXWC/stap_d833fd040735ddde57a23bebb4456542_201.c to 
>> /home/dsmith/.stap_cache/d/8/stap_d833fd040735ddde57a23bebb4456542_201.c
> 
> These messages should probably show up only under -vv (verbosity 2)
> or higher.

Easy enough to fix.  Currently they only show up under '-v'.

>> [...]
>> # stap -v -e 'probe begin { log("hi") }' [...]
>> Pass 2: analyzed script: 1 probe(s), 1 function(s), 0 global(s) in 
>> 10usr/0sys/11real ms.
>> Using cached result 
>> "/home/dsmith/.stap_cache/d/8/stap_d833fd040735ddde57a23bebb4456542_201.ko" 
>> as "/tmp/stapJFisJO/stap_d833fd040735ddde57a23bebb4456542_201.ko"
> 
> This "Using cached result" part could be rephrased as a pair:
> 
>   Pass 3: skipped translation
>   Pass 4: reused cached module stap_deadbeef
> 
>> [...]  A module (currently) gets pulled from the cache after pass 2,
>> even if '-p3' or '-p4' was specified on the command line.
> 
> The translator would still need to spit out (regenerate) the C source
> code for a -p3 run.

Nope.  I actually cache the module and the C file so I can skip pass 3 
but still preserve semantics.

Hmm.  How about something like:

   Pass 3: Using cached 
/home/dsmith/.stap_cache/d/8/stap_d833fd040735ddde57a23bebb4456542_201.c
   Pass 4: Using cached 
/home/dsmith/.stap_cache/d/8/stap_d833fd040735ddde57a23bebb4456542_201.ko

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)