malloc: Add Huge Page support for mmap

With the morecore hook removed, there is not easy way to provide huge
pages support on with glibc allocator without resorting to transparent
huge pages.  And some users and programs do prefer to use the huge pages
directly instead of THP for multiple reasons: no splitting, re-merging
by the VM, no TLB shootdowns for running processes, fast allocation
from the reserve pool, no competition with the rest of the processes
unlike THP, no swapping all, etc.

This patch extends the 'glibc.malloc.hugetlb' tunable: the value
'2' means to use huge pages directly with the system default size,
while a positive value means and specific page size that is matched
against the supported ones by the system.

Currently only memory allocated on sysmalloc() is handled, the arenas
still uses the default system page size.

To test is a new rule is added tests-malloc-hugetlb2, which run the
addes tests with the required GLIBC_TUNABLE setting.  On systems without
a reserved huge pages pool, is just stress the mmap(MAP_HUGETLB)
allocation failure.  To improve test coverage it is required to create
a pool with some allocated pages.

Checked on x86_64-linux-gnu.

Reviewed-by: DJ Delorie <dj@redhat.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/malloc/Makefile b/malloc/Makefile
index 0137595..e9a6666 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -78,9 +78,9 @@ tests-exclude-malloc-check = tst-malloc-check tst-malloc-usable \
 tests-malloc-check = $(filter-out $(tests-exclude-malloc-check) \
 				  $(tests-static),$(tests))
 
-# Run all testes with GLIBC_TUNABLES=glibc.malloc.hugetlb=1 that check the
-# Transparent Huge Pages support.  We need exclude some tests that define
-# the ENV vars.
+# Run all tests with GLIBC_TUNABLES=glibc.malloc.hugetlb={1,2} which check
+# the Transparent Huge Pages support (1) or automatic huge page support (2).
+# We need exclude some tests that define the ENV vars.
 tests-exclude-hugetlb1 = \
 	tst-compathooks-off \
 	tst-compathooks-on \
@@ -93,6 +93,8 @@ tests-exclude-hugetlb1 = \
 	tst-mallocstate
 tests-malloc-hugetlb1 = \
 	$(filter-out $(tests-exclude-hugetlb1), $(tests))
+tests-malloc-hugetlb2 = \
+	$(filter-out $(tests-exclude-hugetlb1), $(tests))
 
 # -lmcheck needs __malloc_initialize_hook, which was deprecated in 2.24.
 ifeq ($(have-GLIBC_2.23)$(build-shared),yesyes)