From bcd9f13b49e57b3b7579e01d8330cc5cd9cab9a1 Mon Sep 17 00:00:00 2001
From: Diogo Netto <61364108+d-netto@users.noreply.github.com>
Date: Sat, 20 Apr 2024 14:09:35 -0300
Subject: [PATCH] add function to query GC page size (#54115) (#147)

---
 src/gc-pages.c |  5 +++++
 test/gc.jl     | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/gc-pages.c b/src/gc-pages.c
index 40e5454136148..4c27e5a097e58 100644
--- a/src/gc-pages.c
+++ b/src/gc-pages.c
@@ -9,6 +9,11 @@
 extern "C" {
 #endif
 
+JL_DLLEXPORT uint64_t jl_get_pg_size(void)
+{
+    return GC_PAGE_SZ;
+}
+
 // Try to allocate memory in chunks to permit faster allocation
 // and improve memory locality of the pools
 #ifdef _P64
diff --git a/test/gc.jl b/test/gc.jl
index e085c1d8658e5..330c136389a4e 100644
--- a/test/gc.jl
+++ b/test/gc.jl
@@ -15,6 +15,19 @@ 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
+
+function run_pg_size_test()
+    page_size = @ccall jl_get_pg_size()::UInt64
+    # supported page sizes: 4KB and 16KB
+    @test page_size == (1 << 12) || page_size == (1 << 14)
+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
@@ -25,3 +38,9 @@ end
     run_gctest("gc/objarray.jl")
     run_gctest("gc/chunks.jl")
 end
+
+@testset "GC page metrics" begin
+    run_nonzero_page_utilization_test()
+    run_pg_size_test()
+end
+