Re: [PATCH net-next v6 0/5] remove page frag implementation in vhost_net

From: Michael S. Tsirkin
Date: Tue Mar 05 2024 - 05:44:30 EST


On Wed, Feb 28, 2024 at 05:30:07PM +0800, Yunsheng Lin wrote:
> 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 patchset 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.

Looks good

Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>



> 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 './vhost_net_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% )
>
> Changelog:
> V6: Add timeout for poll() and simplify some logic as suggested
> by Jason.
>
> V5: Address the comment from jason in vhost_net_test.c and the
> comment about leaving out the gfp change for page frag in
> sock.c as suggested by Paolo.
>
> V4: Resend based on latest net-next branch.
>
> V3:
> 1. Add __page_frag_alloc_align() which is passed with the align mask
> the original function expected as suggested by Alexander.
> 2. Drop patch 3 in v2 suggested by Alexander.
> 3. Reorder patch 4 & 5 in v2 suggested by Alexander.
>
> Note that placing this gfp flags handing for order 3 page in an inline
> function is not considered, as we may be able to unify the page_frag
> and page_frag_cache handling.
>
> V2: Change 'xor'd' to 'masked off', add vhost tx testing for
> vhost_net_test.
>
> V1: Fix some typo, drop RFC tag and rebase on latest net-next.
>
> Yunsheng Lin (5):
> mm/page_alloc: modify page_frag_alloc_align() to accept align as an
> argument
> page_frag: unify gfp bits for order 3 page allocation
> net: introduce page_frag_cache_drain()
> vhost/net: remove vhost_net_page_frag_refill()
> 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 | 16 +-
> mm/page_alloc.c | 22 +-
> net/core/skbuff.c | 9 +-
> tools/virtio/.gitignore | 1 +
> tools/virtio/Makefile | 8 +-
> tools/virtio/linux/virtio_config.h | 4 +
> tools/virtio/vhost_net_test.c | 532 +++++++++++++++++++++
> 12 files changed, 609 insertions(+), 113 deletions(-)
> create mode 100644 tools/virtio/vhost_net_test.c
>
> --
> 2.33.0
>