On Fri, Oct 17, 2008 at 04:39:25PM +0200, Olivier Guilyardi wrote:> Paul Coccoli wrote:> > On Fri, Oct 17, 2008 at 8:46 AM, Paul Davis <paul@xxxxxxxxxxxxxxxxxxxxx> wrote:> >> On Fri, 2008-10-17 at 14:13 +0200, Olivier Guilyardi wrote:> >>> >>> Okay, I wrote such a test. It fails with Jack's ringbuffer (jack1 r3004) but> >>> succeeds with Portaudio's one (r1240).> >> Nice work. Nobody ask why we didn't do this 5 years ago!> > Thanks Paul :)> > >>> >>> The Portaudio code looks more and more robust to me. It's also surprisingly> >>> short. Maybe that the best would be to replace jack's ringbuffer with it? I> >>> think it should be possible to keep the jack_ringbuffer api unchanged.> >> I'd rather add the memory barriers to the JACK code, but this could be a> >> race to see who does what first. A memory barrier is typically single> >> instruction. The complication tends to be defining them in a> >> sufficiently portable way.> >>> > Why do you suspect you need memory barriers? My concern with> > ringbuffer.c is the non-atomic ops on the read and write pointers.> > They're marked volatile, but what I think you really want is make all> > ops on those fields atomic. Stuff like this:> > [...]> > As I said, the Portaudio ringbuffer passes the test even with memory barriers> deactivated. But the lack of memory barriers in jack code was the reason I wrote> this test, please read the whole thread for links to relevant documents.> > Yeah, at PulseAudio they say that the way jack ringbuffer uses volatile is wrong.> > Anyway, I've read a lot of different (and very opposed) point of views on these> matters, and IMO there's nothing like thorough testing to sort this out.> > To figure whether memory barriers are needed or not, we need to run the test on> various architectures.> > For this purpose, I've set up a small svn repo with everything to run the test> easily. There's no dependency, you just need pthread, gcc and sh.> > Here's how to run the test:> > svn co http://svn.samalyse.com/misc/rbtest> cd rbtest> make test> > It tests the ringbuffers from (all included) jack, portaudio and portaudio> without barriers. That can take up to 6 minutes. It has to be a bit long due to> the probabilistic nature of failures.> > LAUsers could you please run this test on various architectures? Especially> PowerPC single-cpu and SMP, x86 single-cpu, SMP, in various flavors, etc... cc -Wall -I. -I./jack -lpthread -o test-int-array-jack \ test-int-array.c jack/ringbuffer.ctest-int-array.c: In function ‘main’:test-int-array.c:113: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’cc -Wall -I. -I./portaudio -lpthread -o test-int-array-portaudio \ test-int-array.c portaudio/ringbuffer.c portaudio/pa_ringbuffer.ctest-int-array.c: In function ‘main’:test-int-array.c:113: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’cc -Wall -I. -I./portaudio -lpthread -o test-int-array-portaudio-nobarrier \ -DNO_MEMORY_BARRIER \ test-int-array.c portaudio/ringbuffer.c portaudio/pa_ringbuffer.ctest-int-array.c: In function ‘main’:test-int-array.c:113: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’cc -Wall -I. -I./jack -lpthread -o test-int-array-jack-fix1 \ test-int-array.c jack/ringbuffer-fix1.ctest-int-array.c: In function ‘main’:test-int-array.c:113: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’ ./alltests.shStarting ringbuffer tests (buffer size: 512) === Jack ringbuffer test ===starting ringbuffer stress test (2 minutes max)buffer size (bytes): 512array size (bytes): 256./alltests.sh: line 9: 7742 Segmentation fault ./test-int-array-jack $BUFFER_SIZE === Jack ringbuffer test (with fix 1) ===starting ringbuffer stress test (2 minutes max)buffer size (bytes): 512array size (bytes): 256./alltests.sh: line 13: 7745 Segmentation fault ./test-int-array-jack-fix1 $BUFFER_SIZE === Portaudio ringbuffer test ===starting ringbuffer stress test (2 minutes max)buffer size (bytes): 512array size (bytes): 256./alltests.sh: line 17: 7748 Segmentation fault ./test-int-array-portaudio $BUFFER_SIZE === Portaudio ringbuffer test (without memory barriers) ===starting ringbuffer stress test (2 minutes max)buffer size (bytes): 512array size (bytes): 256./alltests.sh: line 21: 7751 Segmentation fault ./test-int-array-portaudio-nobarrier $BUFFER_SIZEmake: *** [test] Error 139 Info on the system this was run on, is here:http://restivo.nfshost.com/projects/asus/system-details/ -ken_______________________________________________Linux-audio-user mailing listLinux-audio-user@xxxxxxxxxxxxxxxxxxxxxxxx://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
