[Help-smalltalk] Re: Using COMMON/UNCOMMON

[Paolo Bonzini]

On 02/12/2011 01:28 PM, Holger Hans Peter Freyther wrote:
> Hi Paolo,
> on the hype of the micro benchmarking I started to look at GST (mostly to
> understand the VM and not so much in making it faster). It appears to me that
> when defining COMMON/UNCOMMON to nothing we get a speedup on the
> tinyBenchmark. So this means that either some of the COMMON/UNCOMMOM are
> placed incorrectly, or that the tinyBenchmark is not what we are optimizing
> for and that the COMMON/UNCOMMON are better for some workloads.
>
> Would you be interested in knowing from where this difference is coming? I
> could build with gprof and then use lcov and their branch visualization.
>
>
> holger
>
>
> Before:
> 198180762 bytecodes/sec; 6070565 sends/sec
>
> After:
> 220286113 bytecodes/sec; 6342298 sends/sec

Using master (not a big difference) I'm seeing a marked decrease in 
performance from removing COMMON/UNCOMMON only from libgst/interp.c:

without => 383233532 bytecodes/sec; 10456973 sends/sec
with => 309693028 bytecodes/sec; 9462521 sends/sec

Adding always_inline to unwind_context is faster in the sends benchmark 
(~5%) and doesn't affect the bytecodes benchmark (which hardly execute 
those bytecodes).  I'm applying this:

diff --git a/libgst/interp.c b/libgst/interp.c
index 88080b3..f2be4e2 100644
--- a/libgst/interp.c
+++ b/libgst/interp.c
@@ -472,7 +472,7 @@ static inline void prepare_context (gst_context_part 
context,

 /* Return from the current context and restore the virtual machine's
    status (ip, sp, _gst_this_method, _gst_self, ...).  */
-static void unwind_context (void);
+static void __attribute__ ((__always_inline__)) unwind_context (void);

 /* Check whether it is true that sending SENDSELECTOR to RECEIVER
    accepts NUMARGS arguments.  Note that the RECEIVER is only used to

(F14, 32-bit on 64-bit kernel).

Paolo