Unit Tests fail when configured with --with-lg-page=22

[ghaidinyak]

When I do the following, the unit tests fail. They pass with --with-lg-page=13

./configure --with-lg-page=22
make
make check

[interwq]

I believe it's because the pagesize defined is greater than HUGEPAGE. Do we want to support this @jasone ? Or limit the range of lg-page?

[ghaidinyak]

Where is HUGEPAGE defined and how do I modify it for cross compiling?

[jasone]

Such a large page size is almost certain to work poorly due to external fragmentation. We don't want to do anything special to enable such large pages, though we might consider forcefully limiting it to be no larger than HUGEPAGE.

[ghaidinyak]

Two points, first how is HUGEPAGE defined? X86_64 supports 4K, 2M & 1G huge pages. Powerpc supports 64K, 16M & 16GB pages and ARM supports 64K, 1M & 16M pages.

Second, I tried configuring using --with-lg-page=20 (Hopefully a 2M page) and the unit tests failed. Is a 2MB (typical hugepage on x86_64) supported?

[jasone]

This works:

./configure --with-lg-page=22 --with-lg-hugepage=22 && make all tests && make check

We just need to enforce PAGE <= HUGEPAGE in the configure script.