[PATCH v2 0/2] Add non-blocking stack mempool handler

[Gage Eads <gage.eads@intel.com>]

For some users, the rte ring's "non-preemptive" constraint is not acceptable;
for example, if the application uses a mixture of pinned high-priority threads
and multiplexed low-priority threads that share a mempool.

This patchset introduces a non-blocking stack mempool handler. Note that the
non-blocking algorithm relies on a 128-bit compare-and-swap, so it is limited
to x86_64 machines.

In mempool_perf_autotest the lock-based stack outperforms the non-blocking
handler*, however:
- For applications with preemptible pthreads, a lock-based stack's
  worst-case performance (i.e. one thread being preempted while
  holding the spinlock) is much worse than the non-blocking stack's.
- Using per-thread mempool caches will largely mitigate the performance
  difference.

*Test setup: x86_64 build with default config, dual-socket Xeon E5-2699 v4,
running on isolcpus cores with a tickless scheduler. The lock-based stack's
rate_persec was 1x-3.5x the non-blocking stack's.

v2:
 - Merge separate docs commit into patch #2
 - Fixed two space-after-typecast issues
 - Fix alphabetical sorting for build files
 - Remove unnecessary include path from nb_stack/Makefile
 - Add a comment to nb_lifo_len() justifying its approximate behavior
 - Fix comparison with NULL
 - Remove unnecessary void * cast
 - Fix meson builds and limit them to x86_64
 - Fix missing library error for non-x86_64 builds

Gage Eads (2):
  eal: add 128-bit cmpset (x86-64 only)
  mempool/nb_stack: add non-blocking stack mempool

 MAINTAINERS                                        |   4 +
 config/common_base                                 |   1 +
 doc/guides/prog_guide/env_abstraction_layer.rst    |   5 +
 drivers/mempool/Makefile                           |   3 +
 drivers/mempool/meson.build                        |   5 +
 drivers/mempool/nb_stack/Makefile                  |  23 ++++
 drivers/mempool/nb_stack/meson.build               |   4 +
 drivers/mempool/nb_stack/nb_lifo.h                 | 147 +++++++++++++++++++++
 drivers/mempool/nb_stack/rte_mempool_nb_stack.c    | 125 ++++++++++++++++++
 .../nb_stack/rte_mempool_nb_stack_version.map      |   4 +
 .../common/include/arch/x86/rte_atomic_64.h        |  22 +++
 mk/rte.app.mk                                      |   7 +-
 12 files changed, 348 insertions(+), 2 deletions(-)
 create mode 100644 drivers/mempool/nb_stack/Makefile
 create mode 100644 drivers/mempool/nb_stack/meson.build
 create mode 100644 drivers/mempool/nb_stack/nb_lifo.h
 create mode 100644 drivers/mempool/nb_stack/rte_mempool_nb_stack.c
 create mode 100644 drivers/mempool/nb_stack/rte_mempool_nb_stack_version.map

-- 
2.13.6