I've put in a cumulative of 36 hours guile-2.9.2 multi-threaded stress
testing on two different OS/compiler/glibc combinations, and have seen
exactly zero crashes or hangs so far. So it's perfect. Sorry for earlier
confusion. -- linas
On Sun, May 26, 2019 at 11:40 PM Linas Vepstas <linasveps...@gmail.com>
wrote:
> Andy,
>
> I want to temporarily, maybe permanently retract my last email. I found a
> bug(let) in the intialization of my unit test that appears to maybe account
> for all observed crashes, maybe. I'm re-verifying on multiple machines but
> this will take 24-48 hours. Basically, it looks like guile-2.9.2 is crash
> free (for the last 6 hours) on one os/compiler/glibc combination, I have to
> cross-check on another.
>
> --linas
>
> On Sun, May 26, 2019 at 8:40 AM Linas Vepstas <linasveps...@gmail.com>
> wrote:
>
>> Hi Andy,
>>
>> Thanks! I just tried out the master branch of guile in git (the one
>> tagged v2.9.2). It now passes all of my unit tests. So that's good! ...
>> More or less -- there's still some infrequent multi-threading bug(s). Let
>> me describe.
>>
>> My unit test just transitions C->guile->C and returns, in rapid
>> succession, in 20 threads. So, in pseudocode:
>>
>> SCM do_stuff(SCM a, SCM b) {
>> scm_to_utf8_string(a);
>> scm_to_int(b);
>> ... minor stuff... return scm_from_int(...);
>> }
>> scm_c_define_gsubr("do-things",2,0,0, do_stuff);
>>
>> void thing_doer(int thread_id) {
>> for (i=0; i=15000; i++)
>> char str[100];
>> sprintf(str, "(do-things foo %d)", i);
>> scm_c_catch(scm_eval_string, str);
>> }
>>
>> main () {
>> for (int i=1; i<15; i++) // start 15 threads
>> std::thread(&thing_doer, i);
>> }
>>
>> I'm guessing the above code spends maybe 90% of its time bouncing between
>> guile and C. The string "(do-things foo 42)" changes each time in the loop,
>> so, not sure how the compile vs. interpret tradeoff is done. Either way,
>> its relatively trivial. Likewise, the do_stuff() C routine is fairly thin;
>> after decoding it's args, it doesn't do all that much (sub-microsecond of
>> computing). Based on old, old measurements, scm_eval_string really is the
>> primary CPU consumer, in the 20-microseconds range. Launching 15 threads
>> means that this thing is racing as fast as it can.
>>
>> Anyway, with guile-2.9.2, the above crashes after about 10-15 minutes,
>> either with memory corruption, or with segfault. I worried, so I retested
>> with guile-2.2.4 ... which also crashes, but much much less frequently:
>> seven times in 44 hours wall-clock time (so once ever 6 hours). Which is
>> still more than desired, but...OK.
>>
>> So where's the crash? No clue. Could be my code, could be guile. Since
>> there's a big difference between guile-2.2 and guile-2.9, I'm ready to
>> blame guile. I did try to run it with `valgrind --tool helgrind` and got an
>> ocean of complaints about guile GC, which are probably harmless. I haven't
>> tried to dig deeper yet.
>>
>> -- Linas
>>
>>
>> On Thu, May 23, 2019 at 2:28 PM Andy Wingo <wi...@pobox.com> wrote:
>>
>>> Hi!
>>>
>>> On Thu 06 Dec 2018 06:21, Linas Vepstas <linasveps...@gmail.com> writes:
>>>
>>> > After sending the email below, I scanned the guile-devel archives,
>>> > and I see Thomas Morley talking about Lilypond performance.
>>> > The example program he offers up caught my eye: nested deep
>>> > in a loop is this:
>>> >
>>> > (eval-string "'(a b c)")
>>>
>>> In this case I believe Guile 2.9 / 3 should be significantly faster than
>>> 2.2, because `eval' is compiled to native code rather than bytecode. My
>>> measurements showed it to be on par with the hand-optimized C
>>> implementation from 1.8 and before. Depends of course on how much the
>>> expander is part of your workload, there are differences relative to
>>> Guile 1.8. Anyway, thanks for the note and I just wanted to mention
>>> this point.
>>>
>>> Regarding Scheme -> C++ transitions, there is the possibility that this
>>> too could be much faster with Guile 2.9.x given that these calls are now
>>> JIT-compiled instead of interpreted. We'll have to see.
>>>
>>> Cheers,
>>>
>>> Andy
>>>
>>
>>
>> --
>> cassette tapes - analog TV - film cameras - you
>>
>
>
> --
> cassette tapes - analog TV - film cameras - you
>
--
cassette tapes - analog TV - film cameras - you
