Introduce page_pool support in virtio_net driver to enable page recycling
in RX buffer allocation and avoid repeated page allocator calls. This
applies to mergeable and small buffer modes.
Beyond performance improvements, this patch is a prerequisite for enabling
memory provider-based zero-copy features in virtio_net, specifically devmem
TCP and io_uring ZCRX, which require drivers to use page_pool for buffer
management.
The implementation preserves the DMA premapping optimization introduced in
commit 31f3cd4e5756 ("virtio-net: rq submits premapped per-buffer") by
conditionally using PP_FLAG_DMA_MAP when the virtio backend supports
standard DMA API (vhost, virtio-pci), and falling back to allocation-only
mode for backends with custom DMA mechanisms (VDUSE).
Changes in v2
=============
Addressing reviewer feedback from v1:
- Add "select PAGE_POOL" to Kconfig (Jason Wang)
- Move page pool creation from ndo_open to probe for device lifetime
management (Xuan Zhuo, Jason Wang)
- Implement conditional DMA strategy using virtqueue_dma_dev():
- When non-NULL: use PP_FLAG_DMA_MAP for page_pool-managed DMA premapping
- When NULL (VDUSE): page_pool handles allocation only
- Use page_pool_get_dma_addr() + virtqueue_add_inbuf_premapped() to
preserve DMA premapping optimization from commit 31f3cd4e5756
("virtio-net: rq submits premapped per-buffer") (Jason Wang)
- Remove dual allocation code paths - page_pool now always used for
small/mergeable modes (Jason Wang)
- Remove unused virtnet_rq_alloc/virtnet_rq_init_one_sg functions
- Add comprehensive performance data (Michael S. Tsirkin)
- v1 link:
https://lore.kernel.org/virtualization/[email protected]/
Performance Results
===================
Tested using iperf3 TCP_STREAM with virtio-net on vhost backend.
300-second runs, results show throughput and TCP retransmissions.
The base kernel is synced to net tree and commit: 709bbb015538.
Mergeable Buffer Mode (mrg_rxbuf=on, GSO enabled, MTU 1500):
+--------+---------+---------+------------+------------+--------+--------+
| Queues | Streams | Patch | Throughput | Retries | Delta | Retry% |
+--------+---------+---------+------------+------------+--------+--------+
| 1 | 1 | base | 25.7 Gbps | 0 | - | - |
| 1 | 1 | pp | 26.2 Gbps | 0 | +1.9% | 0% |
+--------+---------+---------+------------+------------+--------+--------+
| 8 | 8 | base | 95.6 Gbps | 236,432 | - | - |
| 8 | 8 | pp | 97.9 Gbps | 188,249 | +2.4% | -20.4% |
+--------+---------+---------+------------+------------+--------+--------+
Small Buffer Mode (mrg_rxbuf=off, GSO disabled, MTU 1500):
+--------+---------+---------+------------+------------+--------+--------+
| Queues | Streams | Patch | Throughput | Retries | Delta | Retry% |
+--------+---------+---------+------------+------------+--------+--------+
| 1 | 1 | base | 9.17 Gbps | 15,152 | - | - |
| 1 | 1 | pp | 9.19 Gbps | 12,203 | +0.2% | -19.5% |
+--------+---------+---------+------------+------------+--------+--------+
| 8 | 8 | base | 43.0 Gbps | 974,500 | - | - |
| 8 | 8 | pp | 44.7 Gbps | 717,411 | +4.0% | -26.4% |
+--------+---------+---------+------------+------------+--------+--------+
Testing
=======
The patches have been tested with:
- iperf3 bulk transfer workloads (multiple queue/stream configurations)
- Included selftests for buffer circulation verification
- Edge case testing: device unbind/bind cycles, rapid interface open/close,
traffic during close, ethtool feature toggling, close with pending refill
work, and data integrity verification
Vishwanath Seshagiri (2):
virtio_net: add page_pool support for buffer allocation
selftests: virtio_net: add buffer circulation test
drivers/net/Kconfig | 1 +
drivers/net/virtio_net.c | 353 ++++++++++--------
.../drivers/net/virtio_net/basic_features.sh | 70 ++++
3 files changed, 273 insertions(+), 151 deletions(-)
--
2.47.3
