add a test for page utilization metric (JuliaLang#52411)

src/gc.c

@@ -2969,7 +2969,7 @@ size_t gc_count_work_in_queue(jl_ptls_t ptls) JL_NOTSAFEPOINT
  * have tried to steal from the queue which still has a work item left, but failed to do so,
  * which violates the semantics of Chase-Lev's work-stealing queue.
  *
- * - Let E1 be the event "master thread writes -1 to gc_master_tid" and E2 be the even
+ * - Let E1 be the event "master thread writes -1 to gc_master_tid" and E2 be the event
  * "master thread observes that `gc_n_threads_marking` is zero". Since we're using
  * sequentially consistent atomics, E1 => E2. Now suppose one thread which is spinning in
  * `gc_should_mark` tries to enter the mark-loop after E2. In order to do so, it must

test/gc.jl

@@ -15,6 +15,13 @@ function run_gctest(file)
  end
 end
 
+function run_nonzero_page_utilization_test()
+ GC.gc()
+ page_utilization = Base.gc_page_utilization_data()
+ # at least one of the pools should have nonzero page_utilization
+ @test any(page_utilization .> 0)
+end
+
 # !!! 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
@@ -24,4 +31,5 @@ end
  run_gctest("gc/linkedlist.jl")
  run_gctest("gc/objarray.jl")
  run_gctest("gc/chunks.jl")
+ run_nonzero_page_utilization_test()
 end