Use mmap(MAP_ANONYMOUS) to allocate queue buffers
Internal buffers for QPs, CQs, SRQs etc. are allocated with
mthca_alloc_buf(), which rounds the buffer's size to the page size and
then allocates page aligned memory using posix_memalign().
However, this allocation is quite wasteful on architectures using 64K
pages (ia64 for example) because we then hit glibc's MMAP_THRESHOLD
malloc parameter and chunks are allocated using mmap. Thus we end up
(requested size rounded to the page size) + (page size) + (malloc overhead)
rounded internally to the page size.
So for example, if we request a buffer of page_size bytes, we end up
consuming 3 pages. In short, for each buffer we allocate, there is an
overhead of 2 pages. This is quite visible on large clusters where
the number of QPs can reach several thousands.
This patch replaces the call to posix_memalign() in mthca_alloc_buf()
with a direct call to mmap().
Signed-off-by: Sebastien Dugue <firstname.lastname@example.org>
Signed-off-by: Roland Dreier <email@example.com>
1 file changed