[Bug kprobes/2062] Return probes does not scale well on SMP box

[jkenisto at us dot ibm dot com]

------- Additional Comments From jkenisto at us dot ibm dot com  2006-04-20 00:22 -------
(In reply to comment #10)
> If it were a matter only of accelerating *allocation* and *deallocation* of the
> kretprobe_instances, sure, per-cpu free_instances pools would be handy.  But the
> code also needs to deal with *lookup*, which needs to search cross-cpus thus a
> shared used_instances.

Insertion, lookup, and removal of a kretprobe_instance is always done by the
task associated with the kretprobe_instance.  So if each task had its own list
of active kretprobe_instances, these activities wouldn't require locking.

Even given the current arrangement (global hash table, hashed by task), we could
lock only the current task's hash bucket, as proposed in Comment #2, and have
fairly low contention.

> 
> Perhaps the single global kretprobe_lock could be replaced with per-kretprobe
locks?

Yeah, Comment #2 proposes that.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=2062

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