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Re: precompiled probing scenarios


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)


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