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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/networking/page_pool.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/networking/page_pool.rst')
-rw-r--r-- | Documentation/networking/page_pool.rst | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/Documentation/networking/page_pool.rst b/Documentation/networking/page_pool.rst new file mode 100644 index 000000000..30f1344e7 --- /dev/null +++ b/Documentation/networking/page_pool.rst @@ -0,0 +1,223 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Page Pool API +============= + +The page_pool allocator is optimized for the XDP mode that uses one frame +per-page, but it can fallback on the regular page allocator APIs. + +Basic use involves replacing alloc_pages() calls with the +page_pool_alloc_pages() call. Drivers should use page_pool_dev_alloc_pages() +replacing dev_alloc_pages(). + +API keeps track of in-flight pages, in order to let API user know +when it is safe to free a page_pool object. Thus, API users +must run page_pool_release_page() when a page is leaving the page_pool or +call page_pool_put_page() where appropriate in order to maintain correct +accounting. + +API user must call page_pool_put_page() once on a page, as it +will either recycle the page, or in case of refcnt > 1, it will +release the DMA mapping and in-flight state accounting. + +Architecture overview +===================== + +.. code-block:: none + + +------------------+ + | Driver | + +------------------+ + ^ + | + | + | + v + +--------------------------------------------+ + | request memory | + +--------------------------------------------+ + ^ ^ + | | + | Pool empty | Pool has entries + | | + v v + +-----------------------+ +------------------------+ + | alloc (and map) pages | | get page from cache | + +-----------------------+ +------------------------+ + ^ ^ + | | + | cache available | No entries, refill + | | from ptr-ring + | | + v v + +-----------------+ +------------------+ + | Fast cache | | ptr-ring cache | + +-----------------+ +------------------+ + +API interface +============= +The number of pools created **must** match the number of hardware queues +unless hardware restrictions make that impossible. This would otherwise beat the +purpose of page pool, which is allocate pages fast from cache without locking. +This lockless guarantee naturally comes from running under a NAPI softirq. +The protection doesn't strictly have to be NAPI, any guarantee that allocating +a page will cause no race conditions is enough. + +* page_pool_create(): Create a pool. + * flags: PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV + * order: 2^order pages on allocation + * pool_size: size of the ptr_ring + * nid: preferred NUMA node for allocation + * dev: struct device. Used on DMA operations + * dma_dir: DMA direction + * max_len: max DMA sync memory size + * offset: DMA address offset + +* page_pool_put_page(): The outcome of this depends on the page refcnt. If the + driver bumps the refcnt > 1 this will unmap the page. If the page refcnt is 1 + the allocator owns the page and will try to recycle it in one of the pool + caches. If PP_FLAG_DMA_SYNC_DEV is set, the page will be synced for_device + using dma_sync_single_range_for_device(). + +* page_pool_put_full_page(): Similar to page_pool_put_page(), but will DMA sync + for the entire memory area configured in area pool->max_len. + +* page_pool_recycle_direct(): Similar to page_pool_put_full_page() but caller + must guarantee safe context (e.g NAPI), since it will recycle the page + directly into the pool fast cache. + +* page_pool_release_page(): Unmap the page (if mapped) and account for it on + in-flight counters. + +* page_pool_dev_alloc_pages(): Get a page from the page allocator or page_pool + caches. + +* page_pool_get_dma_addr(): Retrieve the stored DMA address. + +* page_pool_get_dma_dir(): Retrieve the stored DMA direction. + +* page_pool_put_page_bulk(): Tries to refill a number of pages into the + ptr_ring cache holding ptr_ring producer lock. If the ptr_ring is full, + page_pool_put_page_bulk() will release leftover pages to the page allocator. + page_pool_put_page_bulk() is suitable to be run inside the driver NAPI tx + completion loop for the XDP_REDIRECT use case. + Please note the caller must not use data area after running + page_pool_put_page_bulk(), as this function overwrites it. + +* page_pool_get_stats(): Retrieve statistics about the page_pool. This API + is only available if the kernel has been configured with + ``CONFIG_PAGE_POOL_STATS=y``. A pointer to a caller allocated ``struct + page_pool_stats`` structure is passed to this API which is filled in. The + caller can then report those stats to the user (perhaps via ethtool, + debugfs, etc.). See below for an example usage of this API. + +Stats API and structures +------------------------ +If the kernel is configured with ``CONFIG_PAGE_POOL_STATS=y``, the API +``page_pool_get_stats()`` and structures described below are available. It +takes a pointer to a ``struct page_pool`` and a pointer to a ``struct +page_pool_stats`` allocated by the caller. + +The API will fill in the provided ``struct page_pool_stats`` with +statistics about the page_pool. + +The stats structure has the following fields:: + + struct page_pool_stats { + struct page_pool_alloc_stats alloc_stats; + struct page_pool_recycle_stats recycle_stats; + }; + + +The ``struct page_pool_alloc_stats`` has the following fields: + * ``fast``: successful fast path allocations + * ``slow``: slow path order-0 allocations + * ``slow_high_order``: slow path high order allocations + * ``empty``: ptr ring is empty, so a slow path allocation was forced. + * ``refill``: an allocation which triggered a refill of the cache + * ``waive``: pages obtained from the ptr ring that cannot be added to + the cache due to a NUMA mismatch. + +The ``struct page_pool_recycle_stats`` has the following fields: + * ``cached``: recycling placed page in the page pool cache + * ``cache_full``: page pool cache was full + * ``ring``: page placed into the ptr ring + * ``ring_full``: page released from page pool because the ptr ring was full + * ``released_refcnt``: page released (and not recycled) because refcnt > 1 + +Coding examples +=============== + +Registration +------------ + +.. code-block:: c + + /* Page pool registration */ + struct page_pool_params pp_params = { 0 }; + struct xdp_rxq_info xdp_rxq; + int err; + + pp_params.order = 0; + /* internal DMA mapping in page_pool */ + pp_params.flags = PP_FLAG_DMA_MAP; + pp_params.pool_size = DESC_NUM; + pp_params.nid = NUMA_NO_NODE; + pp_params.dev = priv->dev; + pp_params.dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE; + page_pool = page_pool_create(&pp_params); + + err = xdp_rxq_info_reg(&xdp_rxq, ndev, 0); + if (err) + goto err_out; + + err = xdp_rxq_info_reg_mem_model(&xdp_rxq, MEM_TYPE_PAGE_POOL, page_pool); + if (err) + goto err_out; + +NAPI poller +----------- + + +.. code-block:: c + + /* NAPI Rx poller */ + enum dma_data_direction dma_dir; + + dma_dir = page_pool_get_dma_dir(dring->page_pool); + while (done < budget) { + if (some error) + page_pool_recycle_direct(page_pool, page); + if (packet_is_xdp) { + if XDP_DROP: + page_pool_recycle_direct(page_pool, page); + } else (packet_is_skb) { + page_pool_release_page(page_pool, page); + new_page = page_pool_dev_alloc_pages(page_pool); + } + } + +Stats +----- + +.. code-block:: c + + #ifdef CONFIG_PAGE_POOL_STATS + /* retrieve stats */ + struct page_pool_stats stats = { 0 }; + if (page_pool_get_stats(page_pool, &stats)) { + /* perhaps the driver reports statistics with ethool */ + ethtool_print_allocation_stats(&stats.alloc_stats); + ethtool_print_recycle_stats(&stats.recycle_stats); + } + #endif + +Driver unload +------------- + +.. code-block:: c + + /* Driver unload */ + page_pool_put_full_page(page_pool, page, false); + xdp_rxq_info_unreg(&xdp_rxq); |