Cherry-picking Ensure that new GC tests actually succeed (#49579)

test/gc.jl

@@ -4,15 +4,22 @@ using Test
 
 function run_gctest(file)
     let cmd = `$(Base.julia_cmd()) --depwarn=error --rr-detach --startup-file=no $file`
-        for test_nthreads in (1, 2, 4)
+        @testset for test_nthreads in (1, 2, 4)
             new_env = copy(ENV)
             new_env["JULIA_NUM_THREADS"] = string(test_nthreads)
             new_env["JULIA_NUM_GC_THREADS"] = string(test_nthreads)
-            @time run(pipeline(setenv(cmd, new_env), stdout = stdout, stderr = stderr))
+            @test success(run(pipeline(setenv(cmd, new_env), stdout = stdout, stderr = stderr)))
         end
     end
 end
 
-@time run_gctest("gc/binarytree.jl")
-@time run_gctest("gc/linkedlist.jl")
-@time run_gctest("gc/objarray.jl")
+# !!! note:
+#     Since we run our tests on 32bit OS as well we confine ourselves
+#     to parameters that allocate about 512MB of objects. Max RSS is lower
+#     than that.
+@testset "GC threads" begin
+    run_gctest("gc/binarytree.jl")
+    run_gctest("gc/linkedlist.jl")
+    run_gctest("gc/objarray.jl")
+    run_gctest("gc/chunks.jl")
+end

test/gc/binarytree.jl

@@ -49,5 +49,6 @@ end #module
 
 using .BinaryTreeMutable
 
-BinaryTreeMutable.binary_trees(devnull, 20)
+# Memory usage is 466MB
+BinaryTreeMutable.binary_trees(devnull, 16)
 GC.gc()

test/gc/chunks.jl

@@ -0,0 +1,17 @@
+# This file is a part of Julia. License is MIT: https://julialang.org/license
+
+# MWE from https://github.com/JuliaLang/julia/issues/49501
+N = 1_000_000  # or larger
+T = BigFloat
+
+struct Q{T}
+    a::T
+    b::T
+end
+
+# Memoy use is ~512MB
+let
+    A = [Q(rand(T), rand(T)) for _ in 1:N]
+end
+
+GC.gc()

test/gc/linkedlist.jl

@@ -8,14 +8,16 @@ mutable struct ListNode
   ListNode(x,y) = new(x,y);
 end
 
-function list(n=128)
+function list(N=16*1024^2)
     start::ListNode = ListNode(1)
     current::ListNode = start
-    for i = 2:(n*1024^2)
+    for i = 2:N
         current = ListNode(i,current)
     end
     return current.key
 end
 
+# Memory use is 512 MB
 _ = list()
+
 GC.gc()

test/gc/objarray.jl

@@ -27,9 +27,10 @@ end
 
 function run(maxsize)
     Threads.@threads for i in 1:maxsize
-        work(i*500)
+        work(i*375)
     end
 end
 
-run(4)
+# Memory usage 581 MB
+@time run(4)
 GC.gc()

test/runtests.jl

@@ -75,6 +75,7 @@ move_to_node1("precompile")
 move_to_node1("SharedArrays")
 move_to_node1("threads")
 move_to_node1("Distributed")
+move_to_node1("gc")
 # Ensure things like consuming all kernel pipe memory doesn't interfere with other tests
 move_to_node1("stress")