[Bug testsuite/13650] New: on rawhide, 'scan_unevictable_pages' warning

[Bug testsuite/13650] New: on rawhide, 'scan_unevictable_pages' warning

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13650

             Bug #: 13650
           Summary: on rawhide, 'scan_unevictable_pages' warning
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: testsuite
        AssignedTo: systemtap@sourceware.org
        ReportedBy: dsmith@redhat.com
    Classification: Unclassified


When running the systemtap.examples/check.exp testcase on
3.3.0-0.rc2.git0.2.fc17.x86_64, I see the following pop up in
/var/log/messages:

----
Feb  1 15:30:58 kvm-rawhide-64-2 kernel: [   <7>[  332.018775]
stap_551dc998a8f546ae21488b0870e1a28e_1012: systemtap: 1.7/0.152, base:
ffffffffa0209000, memory: 21data/20text/5ctx/2058net/9alloc kb, probes: 1
Feb  1 15:31:28 kvm-rawhide-64-2 kernel: cat: The scan_unevictable_pages
sysctl/node-interface has been disabled for lack of a legitimate use case.  If
you have one, please send an email to linux-mm@kvack.org.
----

This warning comes from the warn_scan_unevictable_pages() kernel function
(mm/vmscan.c).  I haven't narrowed down which specific example test causes this
to appear.

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[Bug testsuite/13650] on rawhide, 'scan_unevictable_pages' warning

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13650

--- Comment #1 from David Smith <dsmith at redhat dot com> 2012-02-02 18:20:24 UTC ---
Looks like this comes from 2 example scripts (or would if you got the error
more than once):

general/para-callgraph.stp
general/para-callgraph-verbose.stp

The testcase for both of these does something like the following:

# stap para-callgraph.stp 'kernel.function("*@fs/proc*.c")'
'kernel.function("vfs_read")' -c "cat /proc/sys/vm/* || true"

If a process reads /proc/sys/vm/scan_unevictable_pages, that warning is
generated. On a freshly rebooted rawhide system with that kernel, just doing
the following by hand will cause that warning to appear:

# cat /proc/sys/vm/scan_unevictable_pages

Our options here are to ignore the warning or read a different set of files,
perhaps something in the testsuite directory itself.

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[Bug testsuite/13650] on rawhide, 'scan_unevictable_pages' warning

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13650

David Smith <dsmith at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX

--- Comment #2 from David Smith <dsmith at redhat dot com> 2012-02-02 18:42:12 UTC ---
Since this is just a warning (that only will appear once after a reboot), let's
just ignore this.  Once the /proc/sys/vm/scan_unevictable_pages goes away, so
will the warning.

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