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.
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.
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.