github.com/moarvm/moarvm | IRC logs at colabti.org/irclogger/irclogger_logs/moarvm
Set by AlexDaniel on 12 June 2018.
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nwc10 good *, #moarvm 07:03
(and immediately AFK to get coffee)
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MasterDuke jnthn: not sure exactly what you mean re memory vs speed? we could spesh more of the callsites instead of creating templates? on average i'm likely to choose speed over memory use, especially since these came up with regex/grammar related stuff, which i'd love to get massively faster 08:17
sortiz MasterDuke: I think that I found the problem in github.com/MoarVM/MoarVM/issues/1432, a proposed path in my comment. 08:25
s/path/patch/ 08:26
MasterDuke sortiz: so `d_repr_data` is guaranteed never to be NULL after your patch? in that case i'd change its declaration to not have the ternary that looks like it could be so 08:32
nine MasterDuke: it was never NULL even before the patch 08:34
MasterDuke and it could be removed from the if here github.com/MoarVM/MoarVM/blob/mast...ray.c#L822
well, yeah, s_repr_data was. but could d_repr_data ever be? 08:35
nine no
MasterDuke well then i think its declaration and that if should be changed 08:37
sortiz Before the patch, src was erroneously used in line 815, so d_repr_data was NULL also. 08:41
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nine MasterDuke: one thing I noticed when looking at remove_spesh_optimization_if_it_has_too_many_deopts: the "Invalid owner in item added to GC worklist" errors are always about frame registers. 10:50
tellable6 nine, I'll pass your message to MasterDuke
El_Che hi, moarvm can depend on libzstd-dev. Most distros besides rhel 7, do have it. Is there a big advantage depending on that? If not. I'll rather keep the rakudo pkgs dependency free 11:40
jnthn iirc, it's used for heap snapshots, and without it you get them in an old/deprecated format 11:42
nine Isn't taking care of dependencies exactly what distros are for?
El_Che nine: that isn't the question :_ 11:43
:)
Adding a dependency is OK, just making sure it's worth it. From jnthn's response I gather it is 11:44
jnthn I was going to look into seeing if we can provide that library in source builds also (as we do with other deps), because it's going to be a bit disappointing if we get heap snapshot visualization stuff in Comma and then none of the standard builds / packages support it.
(Because MoarVM was built without the dep)
El_Che for now only ubi:7 (rhel) doesn't seem to have the package
(centos 7 does)
jnthn Ubuntu 16.04 doesn't have it, iirc 11:45
Oh wait, maybe it does
I guess that's out of support already too, or going that way soon :)
jnthn will finally use something more modern soon, because new hardware => gotta install something anyway :) 11:46
El_Che jnthn: it has it, I added to the build process but not yet as a dependency
jnthn OK.
El_Che the new pkg hoster only has "el" for CentOS/RHEL/Amazon so I can not upload both Centos 7 (with the lib) and rhel 7 (without) packages 11:48
nine The openSUSE installation on my desktop is about 20 years old now... got files from 2001 in my /etc and /opt directories 11:49
El_Che rhel 8 has the package
jnthn Lunch time, then some more new-disp hacking this afternoon :) 11:52
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MasterDuke . 12:03
tellable6 2021-02-10T10:50:19Z #moarvm <nine> MasterDuke: one thing I noticed when looking at remove_spesh_optimization_if_it_has_too_many_deopts: the "Invalid owner in item added to GC worklist" errors are always about frame registers.
MasterDuke huh, hadn't noticed that 12:04
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nine Could be coincidence, but I somewhat doubt it. Fits too well with that the branch is about spesh candidates, i.e. frames 12:10
MasterDuke i'll look through frame.c again, see if i spot anything missing 12:11
well this is interesting. i just noticed github.com/MoarVM/MoarVM/blob/mast...frame.c#L7 for the first time so turned it on. now i get a segv almost right away in the nqp build (with it off i get a ways into the nqp build before the panic) 12:18
nine MasterDuke: that seems to throw errors in a normal build of another branch as well 12:21
MasterDuke i changed code inside some `#if MVM_SPESH_CHECK_PRESELECTION`, but never compiled it until now 12:22
might have been in the previous PR. is your branch after that was merged?
oh, there's only that one block 12:24
huh. well i added an `if (cands_and_arg_guards)` to that block, and with MVM_SPESH_CHECK_PRESELECTION turned on i get a ton of output like `Inconsistent spesh preselection of 'as_mast' (111): got 7, not 5` 12:36
ah, get a ton of them on master as well 12:38
and even if i back up to before my convert_MVMSpeshCandidate_to_ REPR PR 12:41
is that a problem?
nine Could be just a "this warrants a look but doesn't necessarily have to be bad" and therefore OK. Or could be the source of those random segfaults we see... Who knows? Oh, jnthn would :) 12:44
MasterDuke looks for that butterfly-shaped spotlight
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jnthn I doubt that'd lead to segfaults, though it is a bit odd 12:54
Oh...hmm
I do wonder if removing specializations could break spesh linking though 12:55
In that we identify which specialized candidate to invoke from another one
And if the indices change I guess that may be bad
MasterDuke hm, where does that linking happen> 12:56
?
jnthn github.com/MoarVM/MoarVM/blob/mast...ze.c#L2110 12:57
MasterDuke ugh 12:58
jnthn I'd forgotten this used indices. That's the only way it could have worked before I guess 12:59
That may well be the problem, anyway 13:00
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jnthn The next question is what to do about it. 13:00
MasterDuke yeah... 13:01
jnthn We probably need this candidate to end up discarded also
(that is, the caller linked to it)
Avoiding the index could be done by sticking the MVMSpeshCandidate we want to call into a spesh slot and then having the index of that be used in the op 13:02
iirc the candidate caries a "I've been invalidated" flag; we could then not use it, and maybe log a deopt on the caller, so that it'll eventually accumulate enough points to be worth throwing out also 13:03
Or we can signal explicitly when we log the fake-deopt of it that it's linked to a dead optimized version so should be more expediently dropped too 13:04
These two could be done separately; the first part is just correctness, the second part is performance 13:05
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MasterDuke so instead of `new_operands[1].lit_i16 = spesh_cand;` have `new_operands[1].lit_i16 = MVM_spesh_add_spesh_slot_try_reuse(tc, g, target_sf->body.spesh->body.spesh_candidates[spesh_cand]);`? 13:10
nine like that
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jnthn Yes, then you'll need to also update sp_invoke_* in interp.c and their JIT 13:11
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jnthn ...that's an odd new kind of spam 13:12
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lizmat yeah, looks like it is testing the waters ?
MasterDuke cool, i'll give that a go
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lizmat just pushed some commits making the Spesh Log report also include slow specializations 13:21
gist.github.com/lizmat/654d3658482...c104cca99b
hope this can be useful for folks around here... and if there are other parts of a spesh log you'd like to see reported like that, please let me know
El_Che what is the "better" REPL helper nowadays? 13:30
both options seem unmaintained 13:32
patrickb What are the options? 13:33
El_Che Linenoise and late drforr's perl5-readline 13:34
MasterDuke lizmat: "Specializations that did *NOT* get JITted (times in us)" shouldn't that be "Routines that..."? 13:35
lizmat I think technically they're frames ? 13:36
El_Che readline is not part of the community modules so it assume it's abandoned after drforr passed
lizmat I thought someone else had taken over Readline ?
fooist ?
El_Che github.com/fooist/perl6-readline 13:38
lizmat afk& 13:40
MasterDuke hm, MVM_frame_invoke is going to have to change to take the actual MVMSpeshCandidate instead of an index too, correct? 13:49
jnthn Yes 13:53
MasterDuke k
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nine Well to me the name spesh_cand already sounded like it'd be a pointer. Nice of you to change reality to match my expectations :D 14:35
jnthn
.oO( I knew it was coming :P )
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MasterDuke waits for the top to wobble 15:10
jnthn The nested resumptions is a bit tricky. 15:12
Hmm. 15:13
moritz I don't really know what you're talking about, but "The nested resumptions is a bit tricky." sounds like quite an understatement :-) 15:16
MasterDuke at first i thought it was a further reference to Inception, but maybe it's about new-disp 15:17
jnthn It's handling the situation where, for example, we make a method call, and that method is wrapped, so callsame is initially about the wrappers, but at some point those are exhausted and we want to go on with the methods bit 15:21
Which is the situation that fired the starting gun on new-disp anyway :)
It's the first thing that causes me to care a lot about order of code-gen in dispatch programs 15:22
Which I'd not quite realized would happen
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jnthn Mostly figured it out, in theory... And down to one screenful of compile errors in the dispatch program production. Need a break... 17:17
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MasterDuke well hello there, nqp just built successfully 20:41
and rakudo 20:46
jnthn Ooh, after the spesh linking fix? 20:49
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nine what a way to keep us in suspense 21:06
jnthn I was doing grocery ordering all this time anyway :) 21:16
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MasterDuke heh, yeah (mostly) 22:22
i stuck the candidate in a spesh slot and made the change to MVM_frame_invoke 22:23
however, i have not yet invalidated the caller or anything like that
i am a little unclear exactly what you meant 22:24
or made the jit changes yet (i've been building/running with the jit disabled this whole time) 22:26
but hey, nqp tests and a spectest all pass 22:33
jnthn++ i don't think i ever would have found that spesh linking problem 22:35
jnthn I only wish I'd thought of it sooner, so you didn't spend so much time trying to figure it ut 23:11
*out
MasterDuke btw, this is interesting. i forgot to run with MVM_JIT_DISABLE=1 when building rakudo and running a spectest, but everything was fine, even though i haven't touched any of the jit code 23:12
jnthn I dunno if FSA debug + Valgrind/ASAN were employed together to hunt this, but you were also a bit unlucky if they were, because I'd have expected an out of bounds somewhere.
And it woulda probably pointed somewhere where it'd have been obvious to me what was going on 23:13
MasterDuke yeah, i've had FSA debug turned on, building with --valgrind, and tried --asan a couple times, but they never revealed anything extra beyond that panic (or the segv in the hash code if GC_DEBUG wasn't 3)
jnthn Odd. I'd have expected we'd have tried to read beyond the end of the candidates array. 23:14
Not always, but at least somewhere
MasterDuke maybe it would have during the rakudo build, lots more removing opts there 23:15
only a couple when building nqp before the segv/panic
guess i could have tried decreasing the number of deopts required for removing an opt
oh well 23:16
so is this github.com/MoarVM/MoarVM/blob/mast...dasc#L3377 not getting hit? because MVM_frame_invoke_code now expects an MVMSpeshCandidate as the last arg, not an MVMuint32 23:18
jnthn I'd be a bit surprised if it's not being 23:19
oh, how do you find the candidate though?
Um, better question: do you look through the candidates list to see if it's there? Or just use it?
If the former then the pointer'd not match 23:20
If the latter, I've no guesses
MasterDuke just use it if not NULL
in the MVM_SPESH_CHECK_PRESELECTION block i look through the list to find its index and compare it to the result of MVM_spesh_arg_guard_run 23:21
gist.github.com/MasterDuke17/c0b51...6cf00808dc is the current diff on top of github.com/MoarVM/MoarVM/pull/1426 23:22
hm, don't think my logic is correct in frame.c 23:28
yeah, i was never using the passed in spesh_cand 23:33
now immediate segv
but it was removing candidates before, so that part is working 23:34
jnthn Ah! Only with JIT, or always?
MasterDuke jit disabled
yeah, this spesh_cand looks off 23:38
$1 = {common = {header = {sc_forward_u = {forwarder = 0xffffffff00000003, sc = {sc_idx = 3, idx = 4294967295}, st = 0xffffffff00000003}, owner = 1, flags1 = 1 '\001', flags2 = 2 '\002', size = 24}, st = 0x5555555939f8}, body = {
    cs = 0xffffffff00000003, type_tuple = 0x18020100000001, discarded = 192 '\300', bytecode_size = 21845, bytecode = 0xffffffff00000003 <error: Cannot access memory at address 0xffffffff00000003>, handlers = 0x18020100000001,
    spesh_slots = 0x555555593b88, num_spesh_slots = 3, num_deopts = 4294967295, deopts = 0x18020100000001, deopt_count = 1431911504, deopt_named_used_bit_field = 18446744069414584323, deopt_pea = {materialize_info = 0x18020100000001,
      materialize_info_num = 93824992492824, materialize_info_alloc = 18446744069414584324, deopt_point = 0x18020100000001, deopt_point_num = 93824992493024, deopt_point_alloc = 18446744069414584327}, num_inlines = 1,
    inlines = 0x555555593ea8, local_types = 0xffffffff00000007, lexical_types = 0x18020100000001, num_locals = 16240, num_lexicals = 21849, work_size = 21845, env_size = 7, num_handlers = 4294967295, jitcode = 0x18020100000001,
    deopt_usage_info = 0x555555594038}}
MVM_frame_invoke was called from the interpreter's sp_fastinvoke_o 23:40
jnthn Uff, yeah. Do you MVMROOT the spesh_cand in the case there's a heap allocated frame? 23:42
MasterDuke gist.github.com/MasterDuke17/c0b51...h-L97-L103 ? 23:43
jnthn The interp.c changes look legit at least 23:44
ah, yes
MasterDuke hm, but i need to add spesh_cand to every MVMROOT above there, don't i? 23:45
jnthn Yeah, but also I'm tired so maybe not reading this correctly but I'm not sure where you end up using the provided spesh_cand? 23:46
MasterDuke gist.github.com/MasterDuke17/c0b51...patch-L112 23:47
jnthn Yeah, but that's conditional on: 23:48
if (chosen_spesh_cand_index >= 0 && chosen_spesh_cand_index < (MVMint32)spesh->body.num_spesh_candidates && cands_and_arg_guards) {
I don't think that comes out true if we are given a spesh_cand already?
Or rather, it only happens if MVM_SPESH_CHECK_PRESELECTION is turned on, I think 23:49
MasterDuke i just changed that to `if (spesh_cand || (chosen_spesh_cand_index >= 0 && chosen_spesh_cand_index < (MVMint32)spesh->body.num_spesh_candidates && cands_and_arg_guards)) {`
`if (!spesh_cand) spesh_cand = cands_and_arg_guards->spesh_candidates[chosen_spesh_cand_index];`
jnthn aha, ok 23:50
There's probably a neater factoring but I think that's correct at least
MasterDuke huh, adding it to the other MVMROOTs in MVM_frame_invoke didn't change anything
yeah, that will be cleaned up 23:51
jnthn Spesh slot marking shouldn't be the issue
MasterDuke btw, gist updated with what i'm currently running 23:52
jnthn And the setup of it looks right in optimize.c
Does it ever succeed with a passed-in spesh_cand? 23:57
Are we looking at something occasionally wrong with it, or always wrong with it?
MasterDuke i think always wrong, this segv is very early 23:59