mem: reduce memory fragmentation

This patchset is mostly dealing with changes fbarray, but it is actually about reducing fragmentation in Linuxapp memalloc.

We allocate hugepages from lower VA to higher VA. However, our malloc heap allocates addresses from higher VA to lower VA. This results in a situation where, whenever new page is allocated, malloc starts to allocate memory from the top, leaving fragmented space between new allocation's leftover and previous leftover.

Over time, this leads to lots of free elements sitting at page boundaries, small enough to be useful but large enough to have an impact on memory fragmentation in certain circumstances.

To fix this, we need to allocate memory from higher VA first. However, in order to do that, we need the ability to search fbarray in reverse, which is currently not supported. Adding this support is what most of this patchset is about.

First 4 patches fix some issues in existing fbarray implementation and remove some code duplication, preparing for adding of new functionality.

Next 3 patches add new functionality - reverse search of used/free slots, mirroring already existing functionality in semantics and capable of returning identical results but in reverse order.

Patch 8 adds unit tests for fbarray, testing both existing and new functionality.

Finally, patch 9 changes memalloc to look up free slots in memseg list in reverse order. No other changes is necessary, as all other code can handle segments, wherever they are allocated.

Anatoly Burakov (9):
fbarray: fix errno values returned from functions
fbarray: reduce duplication in find_contig code
fbarray: reduce duplication in find_next_n code
fbarray: reduce duplication in find_next code
fbarray: add reverse find_free/used
fbarray: add reverse find n used/free
fbarray: add reverse find contig used/free
test: add fbarray autotests
memalloc: allocate memory in reverse

 lib/librte_eal/common/eal_common_fbarray.c  | 493 ++++++++++++++---
 lib/librte_eal/common/include/rte_fbarray.h | 114 ++++
 lib/librte_eal/linuxapp/eal/eal_memalloc.c  |   3 +-
 lib/librte_eal/rte_eal_version.map          |   6 +
 test/test/Makefile                          |   1 +
 test/test/test_fbarray.c                    | 576 ++++++++++++++++++++
 6 files changed, 1119 insertions(+), 74 deletions(-)
 create mode 100644 test/test/test_fbarray.c

2.17.1