Skip some stock GC-specific tests when using MMTk (JuliaLang#57104)

As noted in JuliaLang#57103, there are a
few tests that are specific to the stock GC and will fail for MMTk. For
now, this PR simply skips those tests when not using the stock GC until
we agree on how to approach the incompatibilities described in the
issue.

Author: udesou

base/Base.jl

@@ -128,6 +128,8 @@ include("sysinfo.jl")
 include("libc.jl")
 using .Libc: getpid, gethostname, time, memcpy, memset, memmove, memcmp
 
+const USING_STOCK_GC = occursin("stock", GC.gc_active_impl())
+
 # These used to be in build_h.jl and are retained for backwards compatibility.
 # NOTE: keep in sync with `libblastrampoline_jll.libblastrampoline`.
 const libblas_name = "libblastrampoline" * (Sys.iswindows() ? "-5" : "")

base/gcutils.jl

@@ -281,4 +281,15 @@ function logging_enabled()
     ccall(:jl_is_gc_logging_enabled, Cint, ()) != 0
 end
 
+"""
+    GC.gc_active_impl()
+
+Return a string stating which GC implementation is being used and possibly
+its version according to the list of supported GCs
+"""
+function gc_active_impl()
+    unsafe_string(ccall(:jl_gc_active_impl, Ptr{UInt8}, ()))
+end
+
+
 end # module GC

base/timing.jl

@@ -109,10 +109,8 @@ function gc_page_utilization_data()
     return Base.unsafe_wrap(Array, page_utilization_raw, JL_GC_N_MAX_POOLS, own=false)
 end
 
-
-const USING_STOCK_GC = occursin("stock", unsafe_string(ccall(:jl_gc_active_impl, Ptr{UInt8}, ())))
 # Full sweep reasons are currently only available for the stock GC
-@static if USING_STOCK_GC
+@static if Base.USING_STOCK_GC
 # must be kept in sync with `src/gc-stock.h``
 const FULL_SWEEP_REASONS = [:FULL_SWEEP_REASON_SWEEP_ALWAYS_FULL, :FULL_SWEEP_REASON_FORCED_FULL_SWEEP,
                             :FULL_SWEEP_REASON_USER_MAX_EXCEEDED, :FULL_SWEEP_REASON_LARGE_PROMOTION_RATE]
@@ -135,7 +133,7 @@ function full_sweep_reasons()
     d = Dict{Symbol, Int64}()
     # populate the dictionary according to the reasons above for the stock GC
     # otherwise return an empty dictionary for now
-    @static if USING_STOCK_GC
+    @static if Base.USING_STOCK_GC
         reason = cglobal(:jl_full_sweep_reasons, UInt64)
         reasons_as_array = Base.unsafe_wrap(Vector{UInt64}, reason, length(FULL_SWEEP_REASONS), own=false)
         for (i, r) in enumerate(FULL_SWEEP_REASONS)

stdlib/Profile/test/allocs.jl

@@ -73,8 +73,14 @@ end
     @test length(first_alloc.stacktrace) > 0
     @test length(string(first_alloc.type)) > 0
 
-    @testset for type in (Task, Vector{Float64},)
-        @test length(filter(a->a.type <: type, profile.allocs)) >= NUM_TASKS
+    # Issue #57103: This test does not work with MMTk because of fastpath
+    # allocation which never calls the allocation profiler.
+    # TODO: We should port these observability tools (e.g. allocation
+    # profiler and heap snapshot) to MMTk
+    @static if Base.USING_STOCK_GC
+        @testset for type in (Task, Vector{Float64},)
+            @test length(filter(a->a.type <: type, profile.allocs)) >= NUM_TASKS
+        end
     end
 
     # TODO: it would be nice to assert that these tasks
@@ -143,6 +149,8 @@ end
     @test length([a for a in prof.allocs if a.type == String]) >= 1
 end
 
+# FIXME: Issue #57103 disabling test for MMTk.
+@static if Base.USING_STOCK_GC
 @testset "alloc profiler catches allocs from codegen" begin
     @eval begin
         struct MyType x::Int; y::Int end
@@ -162,6 +170,7 @@ end
     @test length(prof.allocs) >= 1
     @test length([a for a in prof.allocs if a.type == MyType]) >= 1
 end
+end
 
 @testset "alloc profiler catches allocs from buffer resize" begin
     f(a) = for _ in 1:100; push!(a, 1); end

stdlib/Profile/test/runtests.jl

@@ -344,6 +344,8 @@ end
     @test only(node.down).first == lidict[8]
 end
 
+# FIXME: Issue #57103: heap snapshots are currently not supported in MMTk
+@static if Base.USING_STOCK_GC
 @testset "HeapSnapshot" begin
     tmpdir = mktempdir()
 
@@ -374,6 +376,7 @@ end
     rm(fname)
     rm(tmpdir, force = true, recursive = true)
 end
+end
 
 @testset "PageProfile" begin
     fname = "$(getpid())_$(time_ns())"

test/checked.jl

@@ -331,8 +331,12 @@ end
     @test checked_pow(BigInt(2), 2) == BigInt(4)
     @test checked_pow(BigInt(2), 100) == BigInt(1267650600228229401496703205376)
 
-    # Perf test: Make sure BigInts allocs don't scale with the power:
-    @test @allocations(checked_pow(BigInt(2), 2)) ≈ @allocations(checked_pow(BigInt(2), 10000)) rtol=0.9
+    # FIXME: Issue #57103: the following test may fail because
+    # allocation may not be logged via MMTk's fastpath allocation
+    @static if Base.USING_STOCK_GC
+        # Perf test: Make sure BigInts allocs don't scale with the power:
+        @test @allocations(checked_pow(BigInt(2), 2)) ≈ @allocations(checked_pow(BigInt(2), 10000)) rtol=0.9
+    end
 end
 
 @testset "Additional tests" begin

test/cmdlineargs.jl

@@ -383,29 +383,33 @@ let exename = `$(Base.julia_cmd()) --startup-file=no --color=no`
         @test p.exitcode == 1 && p.termsignal == 0
     end
 
-    # --gcthreads
-    code = "print(Threads.ngcthreads())"
-    cpu_threads = ccall(:jl_effective_threads, Int32, ())
-    @test string(cpu_threads) ==
-          read(`$exename --threads auto -e $code`, String) ==
-          read(`$exename --threads=auto -e $code`, String) ==
-          read(`$exename -tauto -e $code`, String) ==
-          read(`$exename -t auto -e $code`, String)
-    for nt in (nothing, "1")
-        withenv("JULIA_NUM_GC_THREADS" => nt) do
-            @test read(`$exename --gcthreads=2 -e $code`, String) == "2"
-        end
-        withenv("JULIA_NUM_GC_THREADS" => nt) do
-            @test read(`$exename --gcthreads=2,1 -e $code`, String) == "3"
+    # FIXME: Issue #57103 --gcthreads does not have the same semantics
+    # for Stock GC and MMTk, so the tests below are specific to the Stock GC
+    @static if Base.USING_STOCK_GC
+        # --gcthreads
+        code = "print(Threads.ngcthreads())"
+        cpu_threads = ccall(:jl_effective_threads, Int32, ())
+        @test string(cpu_threads) ==
+            read(`$exename --threads auto -e $code`, String) ==
+            read(`$exename --threads=auto -e $code`, String) ==
+            read(`$exename -tauto -e $code`, String) ==
+            read(`$exename -t auto -e $code`, String)
+        for nt in (nothing, "1")
+            withenv("JULIA_NUM_GC_THREADS" => nt) do
+                @test read(`$exename --gcthreads=2 -e $code`, String) == "2"
+            end
+            withenv("JULIA_NUM_GC_THREADS" => nt) do
+                @test read(`$exename --gcthreads=2,1 -e $code`, String) == "3"
+            end
         end
-    end
 
-    withenv("JULIA_NUM_GC_THREADS" => 2) do
-        @test read(`$exename -e $code`, String) == "2"
-    end
+        withenv("JULIA_NUM_GC_THREADS" => 2) do
+            @test read(`$exename -e $code`, String) == "2"
+        end
 
-    withenv("JULIA_NUM_GC_THREADS" => "2,1") do
-        @test read(`$exename -e $code`, String) == "3"
+        withenv("JULIA_NUM_GC_THREADS" => "2,1") do
+            @test read(`$exename -e $code`, String) == "3"
+        end
     end
 
     # --machine-file
@@ -1182,6 +1186,10 @@ end
     end
 end
 
+# FIXME: Issue #57103: MMTK currently does not use --heap-size-hint since it only
+# supports setting up a hard limit unlike the Stock GC
+# which takes it as a soft limit. For now, we skip the tests below for MMTk
+@static if Base.USING_STOCK_GC
 @testset "heap size hint" begin
     #heap-size-hint, we reserve 250 MB for non GC memory (llvm, etc.)
     @test readchomp(`$(Base.julia_cmd()) --startup-file=no --heap-size-hint=500M -e "println(@ccall jl_gc_get_max_memory()::UInt64)"`) == "$((500-250)*1024*1024)"
@@ -1201,6 +1209,7 @@ end
 
     @test readchomp(`$(Base.julia_cmd()) --startup-file=no --heap-size-hint=10M -e "println(@ccall jl_gc_get_max_memory()::UInt64)"`) == "$(1*1024*1024)"
 end
+end
 
 ## `Main.main` entrypoint
 

test/gc.jl

@@ -67,6 +67,9 @@ end
     run_gctest("gc/chunks.jl")
 end
 
+#FIXME: Issue #57103 disabling tests for MMTk, since
+# they rely on information that is specific to the stock GC.
+@static if Base.USING_STOCK_GC
 @testset "GC page metrics" begin
     run_nonzero_page_utilization_test()
     run_pg_size_test()
@@ -76,13 +79,14 @@ end
     issue_54275_test()
 end
 
-@testset "Base.GC docstrings" begin
-    @test isempty(Docs.undocumented_names(GC))
-end
-
 @testset "Full GC reasons" begin
     full_sweep_reasons_test()
 end
+end
+
+@testset "Base.GC docstrings" begin
+    @test isempty(Docs.undocumented_names(GC))
+end
 
 #testset doesn't work here because this needs to run in top level
 #Check that we ensure objects in toplevel exprs are rooted

test/misc.jl

@@ -1453,7 +1453,8 @@ end
 @test_throws ErrorException finalizer(x->nothing, 1)
 @test_throws ErrorException finalizer(C_NULL, 1)
 
-
+# FIXME: Issue #57103 Test is specific to Stock GC
+@static if Base.USING_STOCK_GC
 @testset "GC utilities" begin
     GC.gc()
     GC.gc(true); GC.gc(false)
@@ -1473,6 +1474,7 @@ end
         @test occursin("GC: pause", read(tmppath, String))
     end
 end
+end
 
 @testset "fieldtypes Module" begin
     @test fieldtypes(Module) === ()