why doesn't yum cache anything?

[Mitch Skinner]

A sample profile of a yum -C list command from my machine (1.4GHz, 1GB
RAM):

         223695 function calls (223189 primitive calls) in 14.600 CPU
seconds

   Ordered by: internal time
   List reduced from 358 to 20 due to restriction <20>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        4    2.150    0.538    2.150    0.538 mdcache.py:58(_unpickle)
        1    1.680    1.680    3.680    3.680 packageSack.py:168
(buildIndexes)
    83615    1.680    0.000    1.680    0.000 packageSack.py:136
(_addToDictAsList)
     3485    1.650    0.000    1.650    0.000 packages.py:402
(importFromDict)
     8149    0.910    0.000    1.390    0.000 packageObject.py:50
(returnNevraTuple)
        1    0.790    0.790    0.810    0.810 __init__.py:59(addDB)
     3485    0.780    0.000    2.820    0.001 packages.py:305(__init__)
     3485    0.770    0.000    0.770    0.000 output.py:43
(simpleProgressBar)
    68424    0.730    0.000    0.730    0.000 packageObject.py:36
(returnSimple)
        1    0.720    0.720    0.720    0.720 __init__.py:88(getHdrList)
        1    0.340    0.340   13.860   13.860 __init__.py:598
(doPackageLists)
        4    0.300    0.075    5.230    1.307 repos.py:40(addDict)
     6090    0.290    0.000    0.290    0.000 packages.py:194(tagByName)
     3485    0.280    0.000    1.220    0.000 packageSack.py:155
(addPackage)
     3485    0.150    0.000    0.150    0.000 packageObject.py:207
(__init__)
     1015    0.100    0.000    0.410    0.000 packages.py:173(__init__)
     6996    0.100    0.000    0.100    0.000 packageObject.py:290
(returnFileEntries)
     2114    0.100    0.000    0.200    0.000 sre.py:177(compile)
        1    0.100    0.100    7.500    7.500 repos.py:164(populateSack)
        2    0.090    0.045    0.090    0.045 packages.py:34
(buildPkgRefDict)

The profile was produced by the bit of python below.  It looks like the
biggest user is _unpickle in mdcache.py, which just calls python's
built-in deserialization that's implemented in C (cPickle), which is
about as close as it gets to pure caching, I think.

I notice that the following two lines are taking up a fair chunk of
time:
        1    1.680    1.680    3.680    3.680 packageSack.py:168
(buildIndexes)
    83615    1.680    0.000    1.680    0.000 packageSack.py:136
(_addToDictAsList)
and it looks like they're (only?) used in dependency solving; could we
leave that work out of commands like list and search?

Certainly, depsolving is a lot faster than it used to be, and I think
the indexing is great if it speeds that up; I just wish I didn't have to
wait for it when I don't need to depsolve.

Mitch

import sys
sys.path.insert(0, '/usr/share/yum-cli')
import yummain
import profile
import pstats

p = profile.Profile()
try:
    p.run('yummain.main(["-C", "list", "*mtr*"])')
except SystemExit, e:
    pass

pst = pstats.Stats(p)
pst.strip_dirs().sort_stats('time').print_stats(20)