[Bug runtime/7016] New: Systemtap will causes OOM when specifying large relay buffer size.

[Bug runtime/7016] New: Systemtap will causes OOM when specifying large relay buffer size.

[mhiramat at redhat dot com]

When I specified larger value than main memory, to -s option of systemtap, the
system ran OOM killer and stopped on ia64 and x86-64. I couldn't reproduce it on
ia32 because it's vmalloc-space is smaller than real memory.

For example, if the machine has 4GB memory, run
# stap -e 'probe begin{hello}' -s 4095
this causes OOM kill.

if the machine has 8GB memory and 4 CPUs, run
# stap -e 'probe begin{hello}' -s 2048 -b

This is always reproducible on 64-bit arch.

I think stap should fail to run if the system doesn't have enough free memory.

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           Summary: Systemtap will causes OOM when specifying large relay
                    buffer size.
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mhiramat at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=7016

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[Bug runtime/7016] Systemtap will causes OOM when specifying large relay buffer size.

[mhiramat at redhat dot com]

------- Additional Comments From mhiramat at redhat dot com  2008-11-10 17:13 -------
Users in stapusr group can cause OOM killer, because the size of relayfs is just
a runtime option of staprun.


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[Bug runtime/7016] Systemtap will causes OOM when specifying large relay buffer size.

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-11-10 18:41 -------
Perhaps relay_open* could be taught to use GFP_ATOMIC | GFP_NORETRY.

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[Bug runtime/7016] Systemtap will causes OOM when specifying large relay buffer size.

[mhiramat at redhat dot com]

------- Additional Comments From mhiramat at redhat dot com  2008-11-10 19:24 -------
(In reply to comment #2)
> Perhaps relay_open* could be taught to use GFP_ATOMIC | GFP_NORETRY.

Indeed. However, we'd better care older kernel too, because relay will be
replaced by new unified trace buffer.
What about checking free memory by using si_meminfo()?

-- 


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