How much is spent in optimizer vs in inference? (Answer: about a half) #1
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KristofferC
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Aug 31, 2022
…Lang#45790) Currently the `@nospecialize`-d `push!(::Vector{Any}, ...)` can only take a single item and we will end up with runtime dispatch when we try to call it with multiple items: ```julia julia> code_typed(push!, (Vector{Any}, Any)) 1-element Vector{Any}: CodeInfo( 1 ─ $(Expr(:foreigncall, :(:jl_array_grow_end), Nothing, svec(Any, UInt64), 0, :(:ccall), Core.Argument(2), 0x0000000000000001, 0x0000000000000001))::Nothing │ %2 = Base.arraylen(a)::Int64 │ Base.arrayset(true, a, item, %2)::Vector{Any} └── return a ) => Vector{Any} julia> code_typed(push!, (Vector{Any}, Any, Any)) 1-element Vector{Any}: CodeInfo( 1 ─ %1 = Base.append!(a, iter)::Vector{Any} └── return %1 ) => Vector{Any} ``` This commit adds a new specialization that it can take arbitrary-length items. Our compiler should still be able to optimize the single-input case as before via the dispatch mechanism. ```julia julia> code_typed(push!, (Vector{Any}, Any)) 1-element Vector{Any}: CodeInfo( 1 ─ $(Expr(:foreigncall, :(:jl_array_grow_end), Nothing, svec(Any, UInt64), 0, :(:ccall), Core.Argument(2), 0x0000000000000001, 0x0000000000000001))::Nothing │ %2 = Base.arraylen(a)::Int64 │ Base.arrayset(true, a, item, %2)::Vector{Any} └── return a ) => Vector{Any} julia> code_typed(push!, (Vector{Any}, Any, Any)) 1-element Vector{Any}: CodeInfo( 1 ─ %1 = Base.arraylen(a)::Int64 │ $(Expr(:foreigncall, :(:jl_array_grow_end), Nothing, svec(Any, UInt64), 0, :(:ccall), Core.Argument(2), 0x0000000000000002, 0x0000000000000002))::Nothing └── goto JuliaLang#7 if not true 2 ┄ %4 = φ (#1 => 1, JuliaLang#6 => %14)::Int64 │ %5 = φ (#1 => 1, JuliaLang#6 => %15)::Int64 │ %6 = Base.getfield(x, %4, true)::Any │ %7 = Base.add_int(%1, %4)::Int64 │ Base.arrayset(true, a, %6, %7)::Vector{Any} │ %9 = (%5 === 2)::Bool └── goto #4 if not %9 3 ─ goto JuliaLang#5 4 ─ %12 = Base.add_int(%5, 1)::Int64 └── goto JuliaLang#5 5 ┄ %14 = φ (#4 => %12)::Int64 │ %15 = φ (#4 => %12)::Int64 │ %16 = φ (#3 => true, #4 => false)::Bool │ %17 = Base.not_int(%16)::Bool └── goto JuliaLang#7 if not %17 6 ─ goto #2 7 ┄ return a ) => Vector{Any} ``` This commit also adds the equivalent implementations for `pushfirst!`.
KristofferC
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Aug 31, 2022
When calling `jl_error()` or `jl_errorf()`, we must check to see if we
are so early in the bringup process that it is dangerous to attempt to
construct a backtrace because the data structures used to provide line
information are not properly setup.
This can be easily triggered by running:
```
julia -C invalid
```
On an `i686-linux-gnu` build, this will hit the "Invalid CPU Name"
branch in `jitlayers.cpp`, which calls `jl_errorf()`. This in turn
calls `jl_throw()`, which will eventually call `jl_DI_for_fptr` as part
of the backtrace printing process, which fails as the object maps are
not fully initialized. See the below `gdb` stacktrace for details:
```
$ gdb -batch -ex 'r' -ex 'bt' --args ./julia -C invalid
...
fatal: error thrown and no exception handler available.
ErrorException("Invalid CPU name "invalid".")
Thread 1 "julia" received signal SIGSEGV, Segmentation fault.
0xf75bd665 in std::_Rb_tree<unsigned int, std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo>, std::_Select1st<std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo> >, std::greater<unsigned int>, std::allocator<std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo> > >::lower_bound (__k=<optimized out>, this=0x248) at /usr/local/i686-linux-gnu/include/c++/9.1.0/bits/stl_tree.h:1277
1277 /usr/local/i686-linux-gnu/include/c++/9.1.0/bits/stl_tree.h: No such file or directory.
#0 0xf75bd665 in std::_Rb_tree<unsigned int, std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo>, std::_Select1st<std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo> >, std::greater<unsigned int>, std::allocator<std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo> > >::lower_bound (__k=<optimized out>, this=0x248) at /usr/local/i686-linux-gnu/include/c++/9.1.0/bits/stl_tree.h:1277
#1 std::map<unsigned int, JITDebugInfoRegistry::ObjectInfo, std::greater<unsigned int>, std::allocator<std::pair<unsigned int const, JITDebugInfoRegistry::ObjectInfo> > >::lower_bound (__x=<optimized out>, this=0x248) at /usr/local/i686-linux-gnu/include/c++/9.1.0/bits/stl_map.h:1258
#2 jl_DI_for_fptr (fptr=4155049385, symsize=symsize@entry=0xffffcfa8, slide=slide@entry=0xffffcfa0, Section=Section@entry=0xffffcfb8, context=context@entry=0xffffcf94) at /cache/build/default-amdci5-4/julialang/julia-master/src/debuginfo.cpp:1181
#3 0xf75c056a in jl_getFunctionInfo_impl (frames_out=0xffffd03c, pointer=4155049385, skipC=0, noInline=0) at /cache/build/default-amdci5-4/julialang/julia-master/src/debuginfo.cpp:1210
#4 0xf7a6ca98 in jl_print_native_codeloc (ip=4155049385) at /cache/build/default-amdci5-4/julialang/julia-master/src/stackwalk.c:636
JuliaLang#5 0xf7a6cd54 in jl_print_bt_entry_codeloc (bt_entry=0xf0798018) at /cache/build/default-amdci5-4/julialang/julia-master/src/stackwalk.c:657
JuliaLang#6 jlbacktrace () at /cache/build/default-amdci5-4/julialang/julia-master/src/stackwalk.c:1090
JuliaLang#7 0xf7a3cd2b in ijl_no_exc_handler (e=0xf0794010) at /cache/build/default-amdci5-4/julialang/julia-master/src/task.c:605
JuliaLang#8 0xf7a3d10a in throw_internal (ct=ct@entry=0xf070c010, exception=<optimized out>, exception@entry=0xf0794010) at /cache/build/default-amdci5-4/julialang/julia-master/src/task.c:638
JuliaLang#9 0xf7a3d330 in ijl_throw (e=0xf0794010) at /cache/build/default-amdci5-4/julialang/julia-master/src/task.c:654
JuliaLang#10 0xf7a905aa in ijl_errorf (fmt=fmt@entry=0xf7647cd4 "Invalid CPU name \"%s\".") at /cache/build/default-amdci5-4/julialang/julia-master/src/rtutils.c:77
JuliaLang#11 0xf75a4b22 in (anonymous namespace)::createTargetMachine () at /cache/build/default-amdci5-4/julialang/julia-master/src/jitlayers.cpp:823
JuliaLang#12 JuliaOJIT::JuliaOJIT (this=<optimized out>) at /cache/build/default-amdci5-4/julialang/julia-master/src/jitlayers.cpp:1044
JuliaLang#13 0xf7531793 in jl_init_llvm () at /cache/build/default-amdci5-4/julialang/julia-master/src/codegen.cpp:8585
JuliaLang#14 0xf75318a8 in jl_init_codegen_impl () at /cache/build/default-amdci5-4/julialang/julia-master/src/codegen.cpp:8648
JuliaLang#15 0xf7a51a52 in jl_restore_system_image_from_stream (f=<optimized out>) at /cache/build/default-amdci5-4/julialang/julia-master/src/staticdata.c:2131
JuliaLang#16 0xf7a55c03 in ijl_restore_system_image_data (buf=0xe859c1c0 <jl_system_image_data> "8'\031\003", len=125161105) at /cache/build/default-amdci5-4/julialang/julia-master/src/staticdata.c:2184
JuliaLang#17 0xf7a55cf9 in jl_load_sysimg_so () at /cache/build/default-amdci5-4/julialang/julia-master/src/staticdata.c:424
JuliaLang#18 ijl_restore_system_image (fname=0x80a0900 "/build/bk_download/julia-d78fdad601/lib/julia/sys.so") at /cache/build/default-amdci5-4/julialang/julia-master/src/staticdata.c:2157
JuliaLang#19 0xf7a3bdfc in _finish_julia_init (rel=rel@entry=JL_IMAGE_JULIA_HOME, ct=<optimized out>, ptls=<optimized out>) at /cache/build/default-amdci5-4/julialang/julia-master/src/init.c:741
JuliaLang#20 0xf7a3c8ac in julia_init (rel=<optimized out>) at /cache/build/default-amdci5-4/julialang/julia-master/src/init.c:728
JuliaLang#21 0xf7a7f61d in jl_repl_entrypoint (argc=<optimized out>, argv=0xffffddf4) at /cache/build/default-amdci5-4/julialang/julia-master/src/jlapi.c:705
JuliaLang#22 0x080490a7 in main (argc=3, argv=0xffffddf4) at /cache/build/default-amdci5-4/julialang/julia-master/cli/loader_exe.c:59
```
To prevent this, we simply avoid calling `jl_errorf` this early in the
process, punting the problem to a later PR that can update guard
conditions within `jl_error*`.
vtjnash
pushed a commit
that referenced
this pull request
Sep 27, 2023
This makes it easier to correlate LLVM IR with the originating source
code by including both argument name and argument type in the LLVM
argument variable.
<details>
<summary>Example 1</summary>
```julia
julia> function f(a, b, c, d, g...)
e = a + b + c + d
f = does_not_exist(e) + e
f
end
f (generic function with 1 method)
julia> @code_llvm f(0,0,0,0,0)
```
```llvm
; @ REPL[1]:1 within `f`
define nonnull {}* @julia_f_141(i64 signext %"a::Int64", i64 signext %"b::Int64", i64 signext %"c::Int64", i64 signext %"d::Int64", i64 signext %"g[0]::Int64") #0 {
top:
%0 = alloca [2 x {}*], align 8
%gcframe3 = alloca [4 x {}*], align 16
%gcframe3.sub = getelementptr inbounds [4 x {}*], [4 x {}*]* %gcframe3, i64 0, i64 0
%1 = bitcast [4 x {}*]* %gcframe3 to i8*
call void @llvm.memset.p0i8.i64(i8* align 16 %1, i8 0, i64 32, i1 true)
%thread_ptr = call i8* asm "movq %fs:0, $0", "=r"() JuliaLang#7
%tls_ppgcstack = getelementptr i8, i8* %thread_ptr, i64 -8
%2 = bitcast i8* %tls_ppgcstack to {}****
%tls_pgcstack = load {}***, {}**** %2, align 8
; @ REPL[1]:3 within `f`
%3 = bitcast [4 x {}*]* %gcframe3 to i64*
store i64 8, i64* %3, align 16
%4 = getelementptr inbounds [4 x {}*], [4 x {}*]* %gcframe3, i64 0, i64 1
%5 = bitcast {}** %4 to {}***
%6 = load {}**, {}*** %tls_pgcstack, align 8
store {}** %6, {}*** %5, align 8
%7 = bitcast {}*** %tls_pgcstack to {}***
store {}** %gcframe3.sub, {}*** %7, align 8
%Main.does_not_exist.cached = load atomic {}*, {}** @0 unordered, align 8
%iscached.not = icmp eq {}* %Main.does_not_exist.cached, null
br i1 %iscached.not, label %notfound, label %found
notfound: ; preds = %top
%Main.does_not_exist.found = call {}* @ijl_get_binding_or_error({}* nonnull inttoptr (i64 139831437630272 to {}*), {}* nonnull inttoptr (i64 139831600565400 to {}*))
store atomic {}* %Main.does_not_exist.found, {}** @0 release, align 8
br label %found
found: ; preds = %notfound, %top
%Main.does_not_exist = phi {}* [ %Main.does_not_exist.cached, %top ], [ %Main.does_not_exist.found, %notfound ]
%8 = bitcast {}* %Main.does_not_exist to {}**
%does_not_exist.checked = load atomic {}*, {}** %8 unordered, align 8
%.not = icmp eq {}* %does_not_exist.checked, null
br i1 %.not, label %err, label %ok
err: ; preds = %found
call void @ijl_undefined_var_error({}* inttoptr (i64 139831600565400 to {}*))
unreachable
ok: ; preds = %found
%.sub = getelementptr inbounds [2 x {}*], [2 x {}*]* %0, i64 0, i64 0
; @ REPL[1]:2 within `f`
; ┌ @ operators.jl:587 within `+` @ int.jl:87
%9 = add i64 %"b::Int64", %"a::Int64"
%10 = add i64 %9, %"c::Int64"
; │ @ operators.jl:587 within `+`
; │┌ @ operators.jl:544 within `afoldl`
; ││┌ @ int.jl:87 within `+`
%11 = add i64 %10, %"d::Int64"
%12 = getelementptr inbounds [4 x {}*], [4 x {}*]* %gcframe3, i64 0, i64 3
store {}* %does_not_exist.checked, {}** %12, align 8
; └└└
; @ REPL[1]:3 within `f`
%13 = call nonnull {}* @ijl_box_int64(i64 signext %11)
%14 = getelementptr inbounds [4 x {}*], [4 x {}*]* %gcframe3, i64 0, i64 2
store {}* %13, {}** %14, align 16
store {}* %13, {}** %.sub, align 8
%15 = call nonnull {}* @ijl_apply_generic({}* nonnull %does_not_exist.checked, {}** nonnull %.sub, i32 1)
store {}* %15, {}** %12, align 8
%16 = call nonnull {}* @ijl_box_int64(i64 signext %11)
store {}* %16, {}** %14, align 16
store {}* %15, {}** %.sub, align 8
%17 = getelementptr inbounds [2 x {}*], [2 x {}*]* %0, i64 0, i64 1
store {}* %16, {}** %17, align 8
%18 = call nonnull {}* @ijl_apply_generic({}* inttoptr (i64 139831370516384 to {}*), {}** nonnull %.sub, i32 2)
%19 = load {}*, {}** %4, align 8
%20 = bitcast {}*** %tls_pgcstack to {}**
store {}* %19, {}** %20, align 8
; @ REPL[1]:4 within `f`
ret {}* %18
}
```
</details>
<details>
<summary>Example 2</summary>
```julia
julia> function g(a, b, c, d; kwarg=0)
a + b + c + d + kwarg
end
g (generic function with 1 method)
julia> @code_llvm g(0,0,0,0,kwarg=0)
```
```llvm
; @ REPL[3]:1 within `g`
define i64 @julia_g_160([1 x i64]* nocapture noundef nonnull readonly align 8 dereferenceable(8) %"#1::NamedTuple", i64 signext %"a::Int64", i64 signext %"b::Int64", i64 signext %"c::Int64", i64 signext %"d::Int64") #0 {
top:
%0 = getelementptr inbounds [1 x i64], [1 x i64]* %"#1::NamedTuple", i64 0, i64 0
; ┌ @ REPL[3]:2 within `#g#1`
; │┌ @ operators.jl:587 within `+` @ int.jl:87
%1 = add i64 %"b::Int64", %"a::Int64"
%2 = add i64 %1, %"c::Int64"
; ││ @ operators.jl:587 within `+`
; ││┌ @ operators.jl:544 within `afoldl`
; │││┌ @ int.jl:87 within `+`
%3 = add i64 %2, %"d::Int64"
; │││└
; │││ @ operators.jl:545 within `afoldl`
; │││┌ @ int.jl:87 within `+`
%unbox = load i64, i64* %0, align 8
%4 = add i64 %3, %unbox
; └└└└
ret i64 %4
}
```
</details>
vtjnash
added a commit
that referenced
this pull request
Oct 30, 2023
…#51489) This exposes the GC "stop the world" API to the user, for causing a thread to quickly stop executing Julia code. This adds two APIs (that will need to be exported and documented later): ``` julia> @CCall jl_safepoint_suspend_thread(#=tid=#1::Cint, #=magicnumber=#2::Cint)::Cint # roughly tkill(1, SIGSTOP) julia> @CCall jl_safepoint_resume_thread(#=tid=#1::Cint)::Cint # roughly tkill(1, SIGCONT) ``` You can even suspend yourself, if there is another task to resume you 10 seconds later: ``` julia> ccall(:jl_enter_threaded_region, Cvoid, ()) julia> t = @task let; Libc.systemsleep(10); print("\nhello from $(Threads.threadid())\n"); @CCall jl_safepoint_resume_thread(0::Cint)::Cint; end; ccall(:jl_set_task_tid, Cint, (Any, Cint), t, 1); schedule(t); julia> @time @CCall jl_safepoint_suspend_thread(0::Cint, 2::Cint)::Cint hello from 2 10 seconds (6 allocations: 264 bytes) 1 ``` The meaning of the magic number is actually the kind of stop that you want: ``` // n.b. suspended threads may still run in the GC or GC safe regions // but shouldn't be observable, depending on which enum the user picks (only 1 and 2 are typically recommended here) // waitstate = 0 : do not wait for suspend to finish // waitstate = 1 : wait for gc_state != 0 (JL_GC_STATE_WAITING or JL_GC_STATE_SAFE) // waitstate = 2 : wait for gc_state != 0 (JL_GC_STATE_WAITING or JL_GC_STATE_SAFE) and that GC is not running on that thread // waitstate = 3 : wait for full suspend (gc_state == JL_GC_STATE_WAITING) -- this may never happen if thread is sleeping currently // if another thread comes along and calls jl_safepoint_resume, we also return early // return new suspend count on success, 0 on failure ``` Only magic number 2 is currently meaningful to the user though. The difference between waitstate 1 and 2 is only relevant in C code which is calling this from JL_GC_STATE_SAFE, since otherwise it is a priori known that GC isn't running, else we too would be running the GC. But the distinction of those states might be useful if we have a concurrent collector. Very important warning: if the stopped thread is holding any locks (e.g. for codegen or types) that you then attempt to acquire, your thread will deadlock. This is very likely, unless you are very careful. A future update to this API may try to change the waitstate to give the option to wait for the thread to release internal or known locks.
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I patched the compiler with simple timing instrumentation.
Then, after first precompiling Plots and GR I removed just Plots:
Just precompiling Plots shows me
which indicates:
inf=23.0033577: 23 seconds spent in inference and optimizeropt=8.303108823: 8 seconds spent in optimizerratio=0.36095203714542945: 36% is in optimizermeanopt=0.00011737833728688966: average second took in optimizer for each functionActually running
plotshows a higher ratio:Eyeballing the outputs from the precompilation of other packages, it looks like it typically ranges from 40% to 60% are spent in the optimizer. So, I guess "about a half" is probably a good rough idea.