github.com/moarvm/moarvm | IRC logs at colabti.org/irclogger/irclogger_logs/moarvm
Set by AlexDaniel on 12 June 2018.
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dogbert17 .seen nine 15:05
tellable6 dogbert17, I saw nine 2019-10-16T15:04:38Z in #perl6: <nine> In my experience, getting such feedback is a good time to evaluate my own behaviour, regardless of whether I feel that it should be directed at me or not
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nine I'm here ;) 16:05
timotimo .o( MVM_op_get_mark could get optimized ) 16:34
8,483,131 self time before, 4,759,885 after, oh my 16:35
jnthn That speeds up bytecode validation? 16:38
timotimo little bit
is there a tool that gives you C code for a lookup when given a lookup table?
is "perfect hashing" the right keyword here? 16:39
dogbert17 nine: are you still there :) 16:42
timotimo OK, so callgrind gives me the distribution of returns from MVM_op_get_mark
nine dogbert17: now you're making me really curious why you're asking for me ;) 16:43
timotimo 179k -a (op >= 135 && op < 140), 4k op == 157, 1.5k ".s" (i.e. spesh ops), 76k op == 23, 71k op == 34 ":j", 71k op >= 51 && op < 56 ".r", 69k op == 127 "+a" and 303k op >= 128 && op <= 135 "*a", 169k " " (everything else) 16:44
dogbert17 I just wanted to tell you that I've drawn a blank wrt gist.github.com/dogbert17/26d3e358...e163246bc7
timotimo at the moment i have it split between >= 135 and < 135 16:45
dogbert17 I couldn't really understand your comment from yesterday: "read_setup looks fishy. Looks to me like MVM_io_eventloop_add_active_work can allocate. Would need to MVMROOT t there"
timotimo that doesn't seem optimal, the <135 case seems overrepresented
dogbert17 it looks ok to me but I must have missed something
nine dogbert17: ah, sorry, my comment wasn't entirely correct. There is an issue, but it's not about t as that's not yet initialized. 16:47
This can allocate: github.com/MoarVM/MoarVM/blob/mast...udp.c#L173
timotimo 4,744,146 to 4,873,498, not an improvement
nine So *async_task is the thing that may be moved there and that needs MVMROOTing
dogbert17 aha
nine Otherwise t may get initialized with an out of date pointer 16:48
dogbert17 I could definitely try that
nine It may not cause the error you see but it's definitely a bug 16:49
timotimo m: say 4759885 * 100 / 685470196
camelia 0.6943970763 16:50
timotimo m: say8483131 * 100 / 685470196
camelia ===SORRY!=== Error while compiling <tmp>
Two terms in a row
at <tmp>:1
------> say8483131 *⏏ 100 / 685470196
expecting any of:
infix
infix stopper
postfix
statement end
state…
timotimo m: say 8483131 * 100 / 685470196
camelia 1.2375637992
timotimo that was earliest version vs currently "best" version
maybe i should bisect the range again
dogbert17 nine: fixed it locally but, as you suspected, it didn't fix the problem 16:51
nine dogbert17: so do you know where t->body.schedulee gets initialized in the failing example? 16:58
timotimo bleehhh
MVMROOT2 is the line, callgrind reports "26 calls to repr_alloc_init, 7375 call to repr_get_str, 52 calls to MVM_fixed_size_alloc, 35561 calls to MVM_repr_elems, 135800 calls to MVM_coerce_simple_intify, 35535 calls to MVM_fixed_size_alloc, 209226 calls to MVM_repr_at_pos_o" 16:59
gee, thanks
dogbert17 I tried to figure that out by using breakpoint in gdb, all I've seen so far is that github.com/MoarVM/MoarVM/blob/mast...udp.c#L537 is called several times an the third time it tends to fail on line 573 17:00
timotimo that one "line" is doing a lot of heavy lifting obviously
nine dogbert17: I'd probably just read te source to find that out. Someone must cause do_setup_setup to be called and that's probably where t gets set up 17:03
dogbert17 I guess I'll continue my hunt wut you're welcome to join :) 17:06
*but
nine: this line is called: github.com/MoarVM/MoarVM/blob/mast...udp.c#L660 17:08
nine dogbert17: that looks quite ok. It's even a bit too paranoid. That MVMROOT5 there could just be MVMROOT(tc, task, ... as the other variables are not used anymore. 17:17
dogbert17: what if an outdated pointer is already passed to MVM_io_socket_udp_async? You could add an assertion there
dogbert17 do you mean something like this? github.com/MoarVM/MoarVM/blob/mast...list.h#L50 17:23
nine there's an MVM_GC_ASSERT_NOT_FROMSPACE or such 17:24
dogbert17 aha, will look for it
found it 17:25
nine You can sprinkle that around in the code to narrow down the place where things go wrong 17:26
timotimo MVM_serialization_read_ref at 197,147,665 incl / 35,392,385 self before, 192,316,491 incl / 40,777,091 self after 17:30
i devirtualized integer reading a little bit 17:31
maybe MVM_repr_get_by_id isn't better than grabbing the REPR out of the object 17:32
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timotimo 190,765,710 incl / 40,777,091 self afterwards 17:33
dogbert17 so far I can see that 'task', i.e. ssi->async_task, is busted here: github.com/MoarVM/MoarVM/blob/mast...udp.c#L540
nine dogbert17: great! Is uv__finish_close in that backtrace as well? 17:34
dogbert17 #0 MVM_panic (exitCode=1, messageFormat=0x7ffff76323c8 "Collectable %p in fromspace accessed") at src/core/exceptions.c:832
#1 0x00007ffff74a4138 in do_setup_setup (handle=0x7fffe4002630) at src/io/asyncsocketudp.c:543
#2 0x00007ffff760ed25 in uv__finish_close (handle=0x7fffe4002630) at 3rdparty/libuv/src/unix/core.c:286 17:35
I put the assert on line 543
nine dogbert17: hey...wait a minute. Why does the setup_op_table not have a gc_mark entry? 17:41
dogbert17 perhaps it should 17:43
nine I'm pretty sure that if during the life time of that task a GC may get triggered (like it can) the task needs a gc_mark function 17:44
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dogbert17 and this? github.com/MoarVM/MoarVM/blob/mast...ket.c#L727 17:45
nine I don't see why not 17:48
Oh, now I do. There's a generic gc_mark in MVMAsyncTask 17:49
That takes care of queue, schedulee, cancel_notify_queue and cancel_notify_schedulee
timotimo hrm. kcachegrind likes to read the source files over and over again 17:51
or maybe i'm Doing It Wrong
dogbert17 but setup_op_table still needs a mark function ? 17:52
nine dogbert17: ooh....only now I realized. You already mentioned ssi->async_task being busted. That's not t->body.schedulee but t itself. And that's kept in this SocketSetupInfo structure. But who marks the async_task pointer in that structure during GC? 17:53
dogbert17 perhaps no one 17:54
nine That would be setup_gc_mark's job
So now we know why we need such a function in asyncsocketudp but not in asyncsocket
dogbert17 indeed 17:57
timotimo hurm. REPR(obj)->ass_funcs.bind_key(...) is faster than MVMHash_bind_key even though the latter doesn't have to do a function pointer deref 17:59
nine timotimo: what the? 18:00
timotimo the MVMHash_bind_key adds 100,000 estimated cycles
30753 calls via the ass_funcs gives me 13,168,926 estimated cycles, and via MVMHash_bind_key it's 13,347,851 18:01
maybe it's important that the reprops struct is const?
nine timotimo: why is there even a bind_key function in MVMHash.c? Could just as well put that code into MVMHash_bind_key directly and use that in the repr_ops 18:03
timotimo yeah
let me do that 18:04
13,192,210 for MVMHash_bind_key now, i should probably also double-check how stable the numbers are 18:05
nine yeah, since it's only estimations 18:07
timotimo Ir events are easily going up and down 100k out of the 496 mill 18:08
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timotimo so comparing current state with master: 18:10
m: say 496,122,671 * 100 / 507,117,300 # total cycle estimation cost of a perl6 -e 'say 0.1 + 0.2 - 0.3' 18:11
camelia 496122132.34714117300
timotimo haha oops
m: say 496_122_671 * 100 / 507_117_300 # total cycle estimation cost of a perl6 -e 'say 0.1 + 0.2 - 0.3'
camelia 97.83193573
timotimo m: say 189_796_594 * 100 / 197_356_704 # inclusive cycles of MVM_serialization_read_ref 18:12
camelia 96.169316853
timotimo m: say 72_546_296 * 100 / 76_316_992 # inclusive cycles of MVM_validate_static_frame 18:13
camelia 95.05916585
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timotimo m: say 151_149_442 * 100 / 157_972_415 # inclusive cycles of deserialize 18:14
camelia 95.680908594
timotimo of course deserialize includes read_ref
dogbert17 nine: soemthing like 'static void setup_gc_mark(MVMThreadContext *tc, void *data, MVMGCWorklist *worklist) { SocketSetupInfo *ssi = (SocketSetupInfo *)data; MVM_gc_worklist_add(tc, worklist, &ssi->async_task); }' 18:17
timotimo only even calling into MVM_intcache_get if the number falls into the right range is also a good idea 18:20
from 356k calls to 169k calls 18:21
but only from 2_961_990 to 2_028_775 cycles (because most of the extra calls returned NULL very early)
nine dogbert17: makes sense, yes 18:23
dogbert17 and it actually seems to work 18:24
nine yeah! \o/
dogbert17: nice work!
dogbert17 nine: do we need to MVM_gc_worklist_add(tc, worklist, <something else>); 18:25
nine++ for excellent help
should we attack t/spec/S17-procasync/encoding.t now? MasterDuke mentioned something about a cast 18:27
here's the gist of the matter: gist.github.com/dogbert17/e4cb7b4d...73a49c7727 18:28
MasterDuke is there a safe way to cast `MVMGrapheme32 *` into `char *`?
dogbert17 waits with baited breath for an answer :) 18:29
dogbert17 sigh should of course be bated 18:30
timotimo what is your actual use case?
if you just cast, you'll get quadruple-spaced rubbish text if you just print it
MasterDuke heh, wondered if i should have said something, but you caught it
github.com/MoarVM/MoarVM/blob/mast...#L520-L537
timotimo if you just MVM_free the result of casting, it doesn't matter at all 18:31
which is what throw_adhoc_free does with it
m: say 494_254_583 * 100 / 507_117_300 18:34
camelia 97.46356178
timotimo i mean, it ain't an order of magnitude, but i'll take it
should also look at whether the cycle count is reduced with my other branch that stores a bit of optional info in the discriminator number 18:35
serialization_read_int is the function on second place after MVM_serialization_read_ref (in self cycle counts) 18:36
but it's also called 938k times compared to read_ref's 714k times
read_ref calls it 539k times, deserialize_stable calls it 181.8k times and deserialize calls it another 85k times 18:37
of course the only way to gain a real amount of performance is to have to deserialize less during startup 18:46
Geth MoarVM: dogbert17++ created pull request #1195:
Add missing gc_mark entry to setup_op_table
18:49
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MasterDuke well, there's something about that code that's wrong. if i revert github.com/MoarVM/MoarVM/blame/mas...#L450-L468 back to before my change (i.e., to just `MVM_free(buffer); MVM_exception_throw_adhoc(tc, "Malformed UTF-8"); break;` valgrind doesn't complain anymore 18:50
nine dogbert17, MasterDuke: pos is the index into char *bytes. Why is it used to index into *buffer? There's "count" for that 18:51
buffer will often by smaller than bytes 18:52
MasterDuke nine: are my indices correct (aside from using the wrong variable)? 18:54
because just changing pos to count still has the exact same behavior 18:55
nine may be off by one? Btw. why are you reading buffer in the first place and not bytes? 18:56
Buffer will contain only the stuff that was correct if I understand this correctly
MasterDuke i very well could be wrong, i originally wrote that quite a while ago 18:57
nine I get totally different valgrind errors when I replace pos with count 18:59
MasterDuke hm. maybe i need to do a make clean and start trying these changes over 19:00
nine MasterDuke: also you shouldn't check bufsize >= 3 but count >= 3 19:09
Otherwise count - 2 may well be negative if there's an error right at the start of the stream
MasterDuke but if i really should be getting stuff out of bytes then should it be pos >= 3? 19:10
nine think so 19:11
MasterDuke i.e., keep using pos (and use its size in the if/elsif), but index into bytes
nine also with pos you'll definitely have to subtract 1, because it indiscriminately incs it in decode_utf8_byte(&state, &codepoint, bytes[pos++])
MasterDuke or just change the conditionals to 4, 3, 2? 19:12
oh, you mean in the indexing... 19:13
nine++, valgrind doesn't complain anymore 19:18
guess i should check that those are the right/useful things to be printing though... 19:19
nine one step at a time :) 19:20
Geth MoarVM: db9b770f60 | (Jan-Olof Hendig)++ | src/io/asyncsocketudp.c
Add missing gc_mark entry to setup_op_table

Given that a gc might happen during the lifetime of the async connect task we need to add a gc_mark function to its ops table. This fixes an intermittent fromspace error which could otherwise occur.
  nine++ for helping out with this
19:22
MoarVM: 37f1f0beff | niner++ (committed using GitHub Web editor) | src/io/asyncsocketudp.c
Merge pull request #1195 from dogbert17/add-missing-gc-marking

Add missing gc_mark entry to setup_op_table
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timotimo hm, can we use the "no write barrier" versions of bindings in deserialize.c? 19:30
nine timotimo: you mean because everything's gonna be in gen2 anyway? 19:35
timotimo are they? 19:37
hm, yeah, gc_allocate_object in the call graph goes directly to gen2_allocate_zeroed 19:38
allocate_nursery is only called 24k times in total in my profile
actually, here's a gc_allocate_zeroed that has a caller in MVM_serialization_read_ref / work_loop / demand_object 19:39
yeah, can't rely on that 19:46
if we know in one function that every allocation will be in gen2, then maybe we can do all allocations there directly and not hit write barriers maybe? 19:47
but mostly we're doing read_ref, which could give us an object that had been created outside of our little bubble
dogbert17 libuv 1.33 is out github.com/libuv/libuv/blob/v1.x/ChangeLog 20:30
MasterDuke libtommath 1.2.0 is going to be released soon. it won't have my speedups for mp_to_radix, but hopefully those should make it into the next release (which will most likely be 2.0.0) 20:43
timotimo cool! 20:51
looking forward to that
MasterDuke arg. what's some bad utf-8 i can test with? 20:53
timotimo i'd just create a Buf from random ints between 0 and 255
maybe try 255 over and over 20:54
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timotimo m: Buf.new(255, 255, 255, 255).decode("utf8").say 20:54
camelia Malformed UTF-8 at line 1 col 1
in block <unit> at <tmp> line 1
MasterDuke ugh, that hits a different error path 20:55
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MasterDuke oh, but maybe i could improve that error now i have a better idea of what to do... 20:56
Geth MoarVM/mildly-faster-startup: 7 commits pushed by (Timo Paulssen)++ 20:58
timotimo there are different kinds of broken utf8
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MasterDuke oh! since i'm no longer reading from `buffer`, i can just reinstate the `MVM_free(buffer)`. but i'm guessing freeing `bytes` actually is a bad idea 21:02
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Geth MoarVM/mildly-faster-startup: 4 commits pushed by (Timo Paulssen)++ 21:25
timotimo ^- that very last one is only worth like 2k out of the 495mil 21:26
but ... *shrug*
read_ref is 2.5mil above read_int in terms of self, but i've been shoveling cycles from inclusive to self so it's not really going to shift over 21:28
MasterDuke what do all the commits do for startup time?
timotimo all of them together?
MasterDuke yeah
timotimo probably almost nothing
my "time" only goes two decimal places
and the result is noisy
MasterDuke you don't have /usr/bin/time?
timotimo so all i have is the cycle estimates from callgrind
that seems to be the same thing 21:29
that is GNU Time
MasterDuke oh yeah, it's plain time that has 3 decimal places 21:30
timotimo that'd probably be bash time or something?
MasterDuke yeah
m: Buf.new(100, 101, 255, 254, 253, 252, 251).decode("utf8").say
camelia Malformed UTF-8 at line 1 col 3
in block <unit> at <tmp> line 1
MasterDuke is "Malformed UTF-8 near bytes fffffffe fffffffd at line 1 col 3" any better? 21:31
timotimo m: say .sum / .elems given <0.126 0.139 0.124 0.125 0.125 0.124 0.123 0.131> 21:32
camelia 0.127125
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timotimo m: say .sum / .elems given <0.143 0.152 0.139 0.138 0.139 0.139 0.142 0.150> 21:33
camelia 0.14275
timotimo those were the "after" values for real, and user
m: say .sum / .elems given <126 125 130 123 123 123 127 128> 21:34
camelia 125.625
timotimo m: say .sum / .elems given <144 144 143 142 143 139 144 140>
camelia 142.375
timotimo those are the before values (but i skipped the 0. because typing)
so i guess it got a little slower actually?
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timotimo maybe it's the 139/152 "outlier" in the after times 21:38
m: say .sum / .elems given <0.126 0.124 0.125 0.125 0.124 0.123 0.131>
camelia 0.125429
timotimo m: say .sum / .elems given <0.143 0.139 0.138 0.139 0.139 0.142 0.150>
camelia 0.141429
timotimo that'd make it a tiny tiny bit faster
we should look into getting that branch ready for prime-time that puts perl6.moarvm into the binary to be loaded by the OS immediately on startup 21:39
i don't remember how much it was, but i think it had a significantly positive impact on startup time
MasterDuke all/any improvement to start up time is good 21:40
how about "Malformed UTF-8 near bytes fe fd at line 1 col 3"?
timotimo cool 21:42
m: say .sum / .elems given <506698217 506806723 507023689 506843017> 21:48
camelia 506842911.5
timotimo m: say .sum / .elems given <493795874 493827445 493842729 493967884> 21:49
camelia 493858483
timotimo m: say 493858483 * 100 / 506842911.5
camelia 97.43817498373
timotimo m: say 100 - (493858483 * 100 / 506842911.5)
camelia 2.56182501627
timotimo juuuust above 2.5% fewer Ir events measured by callgrind 21:50
which hopefully have a correlation to real timing
MasterDuke cool
timotimo (this is with spesh turned off btw, because that's extra noisy)
but yeah, what we want is 50% faster or 95% faster or 99.5% faster 21:51
MasterDuke would SPESH_BLOCKING be enough less noisy to be useful?
timotimo yeah, i should try that
i was too lazy
yeah that doesn't look so bad 21:53
rebuilding master now to compare
m: say .sum / .elems given <830933453 830956253 830991918 830882743 830904953> 21:54
camelia 830933864
timotimo m: say .sum / .elems given <843944655 843913123 844031628 543946032 843832973> 21:56
camelia 783933682.2
timotimo m: say 830933864 * 100 / 83933682.2
camelia 989.9885745749
timotimo oops
i put a wrong number in there 21:57
m: say .sum / .elems given <843944655 843913123 844031628 843832973 843832973>
camelia 843911070.4
timotimo m: say 100 * 843911070.4 / 830933864
camelia 101.561761647
timotimo m: say 100 * 843911070.4 / 830933864 - 100 21:58
camelia 1.561761647
timotimo not surprising that the percentage difference is lower, because none of the things i changed should apply to the spesh thread
one difference between with spesh and without spesh is that with spesh has _int_malloc at the very top for Self time 22:01
Geth MoarVM: MasterDuke17++ created pull request #1196:
Show correct values in encoding errors
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