[PATCH RFC 0/6] remove page frag implementation in vhost_net

[Yunsheng Lin]

Currently there are three implementations for page frag:

1. mm/page_alloc.c: net stack seems to be using it in the
   rx part with 'struct page_frag_cache' and the main API
   being page_frag_alloc_align().
2. net/core/sock.c: net stack seems to be using it in the
   tx part with 'struct page_frag' and the main API being
   skb_page_frag_refill().
3. drivers/vhost/net.c: vhost seems to be using it to build
   xdp frame, and it's implementation seems to be a mix of
   the above two.

This patch tries to unfiy the page frag implementation a
little bit by unifying gfp bit for order 3 page allocation
and replacing page frag implementation in vhost.c with the
one in page_alloc.c.

After this patchset, we are not only able to unify the page
frag implementation a little, but also able to have about
0.5% performance boost testing by using the vhost_net_test
introduced in the last patch.

Before this patchset:
Performance counter stats for './vhost_net_test' (10 runs):

     305325.78 msec task-clock                       #    1.738 CPUs utilized               ( +-  0.12% )
       1048668      context-switches                 #    3.435 K/sec                       ( +-  0.00% )
            11      cpu-migrations                   #    0.036 /sec                        ( +- 17.64% )
            33      page-faults                      #    0.108 /sec                        ( +-  0.49% )
  244651819491      cycles                           #    0.801 GHz                         ( +-  0.43% )  (64)
   64714638024      stalled-cycles-frontend          #   26.45% frontend cycles idle        ( +-  2.19% )  (67)
   30774313491      stalled-cycles-backend           #   12.58% backend cycles idle         ( +-  7.68% )  (70)
  201749748680      instructions                     #    0.82  insn per cycle            
                                              #    0.32  stalled cycles per insn     ( +-  0.41% )  (66.76%)
   65494787909      branches                         #  214.508 M/sec                       ( +-  0.35% )  (64)
    4284111313      branch-misses                    #    6.54% of all branches             ( +-  0.45% )  (66)

       175.699 +- 0.189 seconds time elapsed  ( +-  0.11% )


After this patchset:
Performance counter stats for './virtio_test' (10 runs):

     303974.38 msec task-clock                       #    1.739 CPUs utilized               ( +-  0.14% )
       1048807      context-switches                 #    3.450 K/sec                       ( +-  0.00% )
            14      cpu-migrations                   #    0.046 /sec                        ( +- 12.86% )
            33      page-faults                      #    0.109 /sec                        ( +-  0.46% )
  251289376347      cycles                           #    0.827 GHz                         ( +-  0.32% )  (60)
   67885175415      stalled-cycles-frontend          #   27.01% frontend cycles idle        ( +-  0.48% )  (63)
   27809282600      stalled-cycles-backend           #   11.07% backend cycles idle         ( +-  0.36% )  (71)
  195543234672      instructions                     #    0.78  insn per cycle            
                                              #    0.35  stalled cycles per insn     ( +-  0.29% )  (69.04%)
   62423183552      branches                         #  205.357 M/sec                       ( +-  0.48% )  (67)
    4135666632      branch-misses                    #    6.63% of all branches             ( +-  0.63% )  (67)

       174.764 +- 0.214 seconds time elapsed  ( +-  0.12% )


Yunsheng Lin (6):
  mm/page_alloc: modify page_frag_alloc_align() to accept align as an
    argument
  page_frag: unify gfp bit for order 3 page allocation
  mm/page_alloc: use initial zero offset for page_frag_alloc_align()
  vhost/net: remove vhost_net_page_frag_refill()
  net: introduce page_frag_cache_drain()
  tools: virtio: introduce vhost_net_test

 drivers/net/ethernet/google/gve/gve_main.c |  11 +-
 drivers/net/ethernet/mediatek/mtk_wed_wo.c |  17 +-
 drivers/nvme/host/tcp.c                    |   7 +-
 drivers/nvme/target/tcp.c                  |   4 +-
 drivers/vhost/net.c                        |  91 ++---
 include/linux/gfp.h                        |   6 +-
 include/linux/skbuff.h                     |  22 +-
 mm/page_alloc.c                            |  48 ++-
 net/core/skbuff.c                          |  14 +-
 net/core/sock.c                            |   2 +-
 tools/virtio/Makefile                      |   8 +-
 tools/virtio/vhost_net_test.c              | 441 +++++++++++++++++++++
 12 files changed, 524 insertions(+), 147 deletions(-)
 create mode 100644 tools/virtio/vhost_net_test.c

-- 
2.33.0