Hi, Masami - masami.hiramatsu.pt wrote:
> [...] > For the safeness of kprobes, I have an idea; introduce a whitelist > for dynamic events. AFAICS, the biggest unstable issue of kprobes > comes from putting *many* probes on the functions called from tracers. Why do you think so? We have had problems with single kprobes in the "wrong" spot. The main reason I showed spraying them widely is to get wide coverage with minimal information/effort, not to suggest that the number of concurrent probes per se is a problem. (We have had systemtap scripts probing some areas of the kernel with thousands of active kprobes, e.g. for statement-by-statement variable-watching jobs, and these have worked fine.) > It doesn't crash the kernel but slows down so much, because every > probes hit many other nested miss-hit probes. (kprobes does have code to detect & handle reentrancy.) > This gives us a big performance impact. [...] Sure, but I'd expect to see pure slowdowns show their impact with time-related problems like watchdogs firing or timeouts. > [...] Then, I'd like to propose this new whitelist feature in > kprobe-tracer (not raw kprobe itself). And a sysctl knob for > disabling the whitelist. That knob will be > /proc/sys/debug/kprobe-event-whitelist and disabling it will mark > kernel tainted so that we can check it from bug reports. How would one assemble a reliable whitelist, if we haven't fully characterized the problems that make the blacklist necessary? - FChE -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
