[PATCH 0/5] vsock: reduce RX per-packet socket overhead

[physicalmtea@gmail.com]

From: Jia Jia <physicalmtea@gmail.com>

This series reduces per-packet socket overhead in the virtio-vsock RX
worker.

Patch 1: separate socket lookup from locked packet processing.

Patch 2: keep one socket lock across a bounded run of established
STREAM/RW packets for the same native socket.

Patch 3: reuse the locked socket for later packets with the same
address tuple.

Patch 4: coalesce default write-space notifications while that
lock is held.

Patch 5: defer the default readable callback until after the batch
unlocks. Custom callbacks retain per-packet notification behavior.

Performance:

Tested on single-stream AF_VSOCK (1 reader on Guest CPU0, virtio-vsock IRQ
on Guest CPU1, fresh QEMU guest per state, 16 balanced AB/BA pairs per
payload).

End-to-end RX throughput (64K receiver buffer, SO_RCVLOWAT=1):

  payload  baseline RX (G/s)  PATCH RX (G/s)  throughput change (95% CI)
  256B     0.5722             1.0286          +79.76% [+75.40%, +84.23%]
  512B     1.1464             1.9779          +72.53% [+69.50%, +75.63%]
  1K       2.2714             3.6368          +60.12% [+56.92%, +63.37%]
  4K       3.9095             7.7160          +97.37% [+92.09%, +102.79%]

Fixed-syscall stress test (receiver buffer = sender write size; RX in G/s):

  payload baseline RX PATCH RX throughput change (95% CI) recv() base/patch
  256B     0.2885       0.6737    +133.50% [+123.58%, +143.86%]  1048577/1048577
  512B     0.5631       1.2091    +114.71% [+104.97%, +124.92%]  1048577/1048577
  1K       1.5361       2.9678    +93.20% [+80.15%, +107.20%]     1048577/1048577
  4K       2.8378       6.1878    +118.05% [+109.15%, +127.33%]  538802/525645

Request-response latency (Ping-Pong RTT, 10,000 requests):

  payload  baseline mean RTT (us)  PATCH mean RTT (us)  change (95% CI)
  256B     126.968                124.541              -1.91% [-3.35%, -0.45%]
  4K       130.362                126.664              -2.84% [-5.12%, -0.50%]

Diagnostic Guest CPU1 system-wide cycles (fixed-64K receiver, with perf):

  Buffer size  baseline cycles/B  PATCH cycles/B  cycles change (95% CI)
  256B     15.287            13.630          -10.84% [-12.51%, -9.14%]
  512B      7.306             6.611           -9.51% [-10.92%, -8.08%]
  1K        3.811             3.458           -9.25% [-10.96%, -7.50%]
  4K        1.850             1.669           -9.75% [-11.78%, -7.67%]

Jia Jia (5):
  vsock: split socket lookup from locked RX processing
  vsock: amortize RX socket locking for stream packets
  vsock: reuse same-flow socket lookup in RX batches
  vsock: coalesce RX write-space notifications in lock batches
  vsock: defer RX readable notifications until batch unlock

 include/linux/virtio_vsock.h            |  14 ++
 include/net/af_vsock.h                  |   3 +
 net/vmw_vsock/af_vsock.c                |   2 +
 net/vmw_vsock/virtio_transport.c        |  48 ++++-
 net/vmw_vsock/virtio_transport_common.c | 341 +++++++++++++++++++++++++++-----
 5 files changed, 357 insertions(+), 51 deletions(-)

base-commit: f5f84daefcd92d7a630066635ecea1433ed5eac7
-- 
2.53.0