133637fcfa
Use the new recycling API for page_pool. In a drop rate test, the packet rate is almost doubled, from 1110 Kpps to 2128 Kpps. perf top on a stock system shows: Overhead Shared Object Symbol 34.88% [kernel] [k] page_pool_release_page 8.06% [kernel] [k] free_unref_page 6.42% [mvpp2] [k] mvpp2_rx 6.07% [kernel] [k] eth_type_trans 5.18% [kernel] [k] __netif_receive_skb_core 4.95% [kernel] [k] build_skb 4.88% [kernel] [k] kmem_cache_free 3.97% [kernel] [k] kmem_cache_alloc 3.45% [kernel] [k] dev_gro_receive 2.73% [kernel] [k] page_frag_free 2.07% [kernel] [k] __alloc_pages_bulk 1.99% [kernel] [k] arch_local_irq_save 1.84% [kernel] [k] skb_release_data 1.20% [kernel] [k] netif_receive_skb_list_internal With packet rate stable at 1100 Kpps: tx: 0 bps 0 pps rx: 532.7 Mbps 1110 Kpps tx: 0 bps 0 pps rx: 532.6 Mbps 1110 Kpps tx: 0 bps 0 pps rx: 532.4 Mbps 1109 Kpps tx: 0 bps 0 pps rx: 532.1 Mbps 1109 Kpps tx: 0 bps 0 pps rx: 531.9 Mbps 1108 Kpps tx: 0 bps 0 pps rx: 531.9 Mbps 1108 Kpps And this is the same output with recycling enabled: Overhead Shared Object Symbol 12.91% [kernel] [k] eth_type_trans 12.54% [mvpp2] [k] mvpp2_rx 9.67% [kernel] [k] build_skb 9.63% [kernel] [k] __netif_receive_skb_core 8.44% [kernel] [k] page_pool_put_page 8.07% [kernel] [k] kmem_cache_free 7.79% [kernel] [k] kmem_cache_alloc 6.86% [kernel] [k] dev_gro_receive 3.19% [kernel] [k] skb_release_data 2.41% [kernel] [k] netif_receive_skb_list_internal 2.18% [kernel] [k] page_pool_refill_alloc_cache 1.76% [kernel] [k] napi_gro_receive 1.61% [kernel] [k] kfree_skb 1.20% [kernel] [k] dma_sync_single_for_device 1.16% [mvpp2] [k] mvpp2_poll 1.12% [mvpp2] [k] mvpp2_read With packet rate above 2100 Kpps: tx: 0 bps 0 pps rx: 1021 Mbps 2128 Kpps tx: 0 bps 0 pps rx: 1021 Mbps 2127 Kpps tx: 0 bps 0 pps rx: 1021 Mbps 2128 Kpps tx: 0 bps 0 pps rx: 1021 Mbps 2128 Kpps tx: 0 bps 0 pps rx: 1022 Mbps 2128 Kpps tx: 0 bps 0 pps rx: 1022 Mbps 2129 Kpps The major performance increase is explained by the fact that the most CPU consuming functions (page_pool_release_page, page_frag_free and free_unref_page) are no longer called on a per packet basis. The test was done by sending to the macchiatobin 64 byte ethernet frames with an invalid ethertype, so the packets are dropped early in the RX path. Signed-off-by: Matteo Croce <mcroce@microsoft.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.