Peter Zijlstra <pet...@infradead.org> writes: > This series is aimed at making __module_address() go fast(er).
Acked-by: Rusty Russell <ru...@rustcorp.com.au> (module parts) Since all the interesting stuff is not module-specific, assume this is via Ingo? Otherwise, I'll take it... Thanks, Rusty. > > The reason for doing so is that most stack unwinders use kernel_text_address() > to validate each frame. Perf and ftrace (can) end up doing a lot of stack > traces from performance sensitive code. > > On the way there it: > - annotates and sanitizes module locking > - introduces the latched RB-tree > - employs it to make __module_address() go fast. > > I've build and boot tested this on x86_64 with modules and lockdep > enabled. Performance numbers (below) are done with lockdep disabled. > > As previously mentioned; the reason for writing the latched RB-tree as generic > code is mostly for clarity/documentation purposes; as there are a number of > separate and non trivial bits to the complete solution. > > As measured on my ivb-ep system with 84 modules loaded; the test module > reports > (cache hot, performance cpufreq): > > avg +- stdev > Before: 611 +- 10 [ns] per __module_address() call > After: 17 +- 5 [ns] per __module_address() call > > PMI measurements for a cpu running loops in a module (also [ns]): > > Before: Mean: 2719 +- 1, Stdev: 214, Samples: 40036 > After: Mean: 947 +- 0, Stdev: 132, Samples: 40037 > > Note; I have also tested things like: perf record -a -g modprobe > mod_test, to make 'sure' to hit some of the more interesting paths. > > Changes since last time: > > - rebased against Rusty's tree > - raw_read_seqcount_latch() -- (mingo) > > Based on rusty/linux.git/pending-rebases; please consider for 4.2 > > Thanks! -- 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/