[Bug kprobes/10839] New: kretprobes use excessive memory on x86_64 rawhide

[jistone at redhat dot com]

Consider the following session on 2.6.31.1-56.fc12.x86_64:

$ MOD=$(stap -e 'probe kernel.function("*@fs/*").return { next }' -p4)
$ free
             total       used       free     shared    buffers     cached
Mem:       1992712     308924    1683788          0       7628     133084
-/+ buffers/cache:     168212    1824500
Swap:       522104          0     522104
$ staprun $MOD -D -o /dev/null
1564
# (give it a moment to load all the probes)
$ free
             total       used       free     shared    buffers     cached
Mem:       1992712    1459972     532740          0       7628     133096
-/+ buffers/cache:    1319248     673464
Swap:       522104          0     522104


That's a 1124MB increase in "used" when the module is loaded!  I bumped my VM up
to 2GB for this test, but normally I run with only 512MB, so scripts were
causing me to get OOM.

For comparison, I get 43MB on 2.6.31.1-56.fc12.i686, and I get 72MB on
2.6.30.8-64.fc11.x86_64.  These numbers still seem high, but they're not so
outrageous...

-- 
           Summary: kretprobes use excessive memory on x86_64 rawhide
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: kprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: jistone at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10839

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