linux huge pages fallback strategy (mjansson#268)

web-logs2 · Dec 16, 2021 · 07975ec · 07975ec
1 parent 4c10723
commit 07975ec
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/rpmalloc/rpmalloc.c b/rpmalloc/rpmalloc.c
@@ -881,6 +881,18 @@ _rpmalloc_mmap_os(size_t size, size_t* offset) {
 	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE, flags, fd, 0);
 #  elif defined(MAP_HUGETLB)
 	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE | PROT_MAX(PROT_READ | PROT_WRITE), (_memory_huge_pages ? MAP_HUGETLB : 0) | flags, -1, 0);
+#    if defined(MADV_HUGEPAGE)
+	// In some configurations, huge pages allocations might fail thus
+	// we fallback to normal allocations and promote the region as transparent huge page
+	if ((ptr == MAP_FAILED || !ptr) && _memory_huge_pages) {
+		ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE, flags, -1, 0);
+		if (ptr && ptr != MAP_FAILED) {
+			int prm = madvise(ptr, size + padding, MADV_HUGEPAGE);
+			(void)prm;
+			rpmalloc_assert((prm == 0), "Failed to promote the page to THP");
+		}
+	}
+#    endif
 #  elif defined(MAP_ALIGNED)
 	const size_t align = (sizeof(size_t) * 8) - (size_t)(__builtin_clzl(size - 1));
 	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE, (_memory_huge_pages ? MAP_ALIGNED(align) : 0) | flags, -1, 0);