kernel/linux.git/include/uapi/linux/pkt_sched.h, branch v6.1.168

net/sched: taprio: allow user input of per-tc max SDU

2022-09-30T01:52:05+00:00

IEEE 802.1Q clause 12.29.1.1 "The queueMaxSDUTable structure and data types" and 8.6.8.4 "Enhancements for scheduled traffic" talk about the existence of a per traffic class limitation of maximum frame sizes, with a fallback on the port-based MTU. As far as I am able to understand, the 802.1Q Service Data Unit (SDU) represents the MAC Service Data Unit (MSDU, i.e. L2 payload), excluding any number of prepended VLAN headers which may be otherwise present in the MSDU. Therefore, the queueMaxSDU is directly comparable to the device MTU (1500 means L2 payload sizes are accepted, or frame sizes of 1518 octets, or 1522 plus one VLAN header). Drivers which offload this are directly responsible of translating into other units of measurement. To keep the fast path checks optimized, we keep 2 arrays in the qdisc, one for max_sdu translated into frame length (so that it's comparable to skb->len), and another for offloading and for dumping back to the user. Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

fq_codel: generalise ce_threshold marking for subset of traffic

2021-10-20T22:24:36+00:00

Commit e72aeb9ee0e3 ("fq_codel: implement L4S style ce_threshold_ect1 marking") expanded the ce_threshold feature of FQ-CoDel so it can be applied to a subset of the traffic, using the ECT(1) bit of the ECN field as the classifier. However, hard-coding ECT(1) as the only classifier for this feature seems limiting, so let's expand it to be more general. To this end, change the parameter from a ce_threshold_ect1 boolean, to a one-byte selector/mask pair (ce_threshold_{selector,mask}) which is applied to the whole diffserv/ECN field in the IP header. This makes it possible to classify packets by any value in either the ECN field or the diffserv field. In particular, setting a selector of INET_ECN_ECT_1 and a mask of INET_ECN_MASK corresponds to the functionality before this patch, and a mask of ~INET_ECN_MASK allows using the selector as a straight-forward match against a diffserv code point: # apply ce_threshold to ECT(1) traffic tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x1/0x3 # apply ce_threshold to ECN-capable traffic marked as diffserv AF22 tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x50/0xfc Regardless of the selector chosen, the normal rules for ECN-marking of packets still apply, i.e., the flow must still declare itself ECN-capable by setting one of the bits in the ECN field to get marked at all. v2: - Add tc usage examples to patch description Signed-off-by: Toke Høiland-Jørgensen Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/20211019174709.69081-1-toke@redhat.com Signed-off-by: Jakub Kicinski

fq_codel: implement L4S style ce_threshold_ect1 marking

2021-10-15T10:33:08+00:00

Add TCA_FQ_CODEL_CE_THRESHOLD_ECT1 boolean option to select Low Latency, Low Loss, Scalable Throughput (L4S) style marking, along with ce_threshold. If enabled, only packets with ECT(1) can be transformed to CE if their sojourn time is above the ce_threshold. Note that this new option does not change rules for codel law. In particular, if TCA_FQ_CODEL_ECN is left enabled (this is the default when fq_codel qdisc is created), ECT(0) packets can still get CE if codel law (as governed by limit/target) decides so. Section 4.3.b of current draft [1] states: b. A scheduler with per-flow queues such as FQ-CoDel or FQ-PIE can be used for L4S. For instance within each queue of an FQ-CoDel system, as well as a CoDel AQM, there is typically also ECN marking at an immediate (unsmoothed) shallow threshold to support use in data centres (see Sec.5.2.7 of [RFC8290]). This can be modified so that the shallow threshold is solely applied to ECT(1) packets. Then if there is a flow of non-ECN or ECT(0) packets in the per-flow-queue, the Classic AQM (e.g. CoDel) is applied; while if there is a flow of ECT(1) packets in the queue, the shallower (typically sub-millisecond) threshold is applied. Tested: tc qd replace dev eth1 root fq_codel ce_threshold_ect1 50usec netperf ... -t TCP_STREAM -- K dctcp tc -s -d qd sh dev eth1 qdisc fq_codel 8022: root refcnt 32 limit 10240p flows 1024 quantum 9212 target 5ms ce_threshold_ect1 49us interval 100ms memory_limit 32Mb ecn drop_batch 64 Sent 14388596616 bytes 9543449 pkt (dropped 0, overlimits 0 requeues 152013) backlog 0b 0p requeues 152013 maxpacket 68130 drop_overlimit 0 new_flow_count 95678 ecn_mark 0 ce_mark 7639 new_flows_len 0 old_flows_len 0 [1] L4S current draft: https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-l4s-arch Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Ingemar Johansson S Cc: Tom Henderson Cc: Bob Briscoe Signed-off-by: David S. Miller

fq_codel: reject silly quantum parameters

2021-09-04T09:49:46+00:00

syzbot found that forcing a big quantum attribute would crash hosts fast, essentially using this: tc qd replace dev eth0 root fq_codel quantum 4294967295 This is because fq_codel_dequeue() would have to loop ~2^31 times in : if (flow->deficit <= 0) { flow->deficit += q->quantum; list_move_tail(&flow->flowchain, &q->old_flows); goto begin; } SFQ max quantum is 2^19 (half a megabyte) Lets adopt a max quantum of one megabyte for FQ_CODEL. Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller

sch_htb: Hierarchical QoS hardware offload

2021-01-23T04:41:29+00:00

HTB doesn't scale well because of contention on a single lock, and it also consumes CPU. This patch adds support for offloading HTB to hardware that supports hierarchical rate limiting. In the offload mode, HTB passes control commands to the driver using ndo_setup_tc. The driver has to replicate the whole hierarchy of classes and their settings (rate, ceil) in the NIC. Every modification of the HTB tree caused by the admin results in ndo_setup_tc being called. After this setup, the HTB algorithm is done completely in the NIC. An SQ (send queue) is created for every leaf class and attached to the hierarchy, so that the NIC can calculate and obey aggregated rate limits, too. In the future, it can be changed, so that multiple SQs will back a single leaf class. ndo_select_queue is responsible for selecting the right queue that serves the traffic class of each packet. The data path works as follows: a packet is classified by clsact, the driver selects a hardware queue according to its class, and the packet is enqueued into this queue's qdisc. This solution addresses two main problems of scaling HTB: 1. Contention by flow classification. Currently the filters are attached to the HTB instance as follows: # tc filter add dev eth0 parent 1:0 protocol ip flower dst_port 80 classid 1:10 It's possible to move classification to clsact egress hook, which is thread-safe and lock-free: # tc filter add dev eth0 egress protocol ip flower dst_port 80 action skbedit priority 1:10 This way classification still happens in software, but the lock contention is eliminated, and it happens before selecting the TX queue, allowing the driver to translate the class to the corresponding hardware queue in ndo_select_queue. Note that this is already compatible with non-offloaded HTB and doesn't require changes to the kernel nor iproute2. 2. Contention by handling packets. HTB is not multi-queue, it attaches to a whole net device, and handling of all packets takes the same lock. When HTB is offloaded, it registers itself as a multi-queue qdisc, similarly to mq: HTB is attached to the netdev, and each queue has its own qdisc. Some features of HTB may be not supported by some particular hardware, for example, the maximum number of classes may be limited, the granularity of rate and ceil parameters may be different, etc. - so, the offload is not enabled by default, a new parameter is used to enable it: # tc qdisc replace dev eth0 root handle 1: htb offload Signed-off-by: Maxim Mikityanskiy Reviewed-by: Tariq Toukan Signed-off-by: Jakub Kicinski

net: sched: sch_red: Add qevents "early_drop" and "mark"

2020-06-30T00:08:28+00:00

In order to allow acting on dropped and/or ECN-marked packets, add two new qevents to the RED qdisc: "early_drop" and "mark". Filters attached at "early_drop" block are executed as packets are early-dropped, those attached at the "mark" block are executed as packets are ECN-marked. Two new attributes are introduced: TCA_RED_EARLY_DROP_BLOCK with the block index for the "early_drop" qevent, and TCA_RED_MARK_BLOCK for the "mark" qevent. Absence of these attributes signifies "don't care": no block is allocated in that case, or the existing blocks are left intact in case of the change callback. For purposes of offloading, blocks attached to these qevents appear with newly-introduced binder types, FLOW_BLOCK_BINDER_TYPE_RED_EARLY_DROP and FLOW_BLOCK_BINDER_TYPE_RED_MARK. Signed-off-by: Petr Machata Signed-off-by: David S. Miller

net_sched: sch_fq: add horizon attribute

2020-05-04T18:56:17+00:00

QUIC servers would like to use SO_TXTIME, without having CAP_NET_ADMIN, to efficiently pace UDP packets. As far as sch_fq is concerned, we need to add safety checks, so that a buggy application does not fill the qdisc with packets having delivery time far in the future. This patch adds a configurable horizon (default: 10 seconds), and a configurable policy when a packet is beyond the horizon at enqueue() time: - either drop the packet (default policy) - or cap its delivery time to the horizon. $ tc -s -d qd sh dev eth0 qdisc fq 8022: root refcnt 257 limit 10000p flow_limit 100p buckets 1024 orphan_mask 1023 quantum 10Kb initial_quantum 51160b low_rate_threshold 550Kbit refill_delay 40.0ms timer_slack 10.000us horizon 10.000s Sent 1234215879 bytes 837099 pkt (dropped 21, overlimits 0 requeues 6) backlog 0b 0p requeues 6 flows 1191 (inactive 1177 throttled 0) gc 0 highprio 0 throttled 692 latency 11.480us pkts_too_long 0 alloc_errors 0 horizon_drops 21 horizon_caps 0 v2: fixed an overflow on 32bit kernels in fq_init(), reported by kbuild test robot Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller

taprio: do not use BIT() in TCA_TAPRIO_ATTR_FLAG_* definitions

2020-03-27T03:08:45+00:00

BIT() macro definition is internal to the Linux kernel and is not to be used in UAPI headers; replace its usage with the _BITUL() macro that is already used elsewhere in the header. Fixes: 9c66d1564676 ("taprio: Add support for hardware offloading") Signed-off-by: Eugene Syromiatnikov Acked-by: Vladimir Oltean Signed-off-by: David S. Miller

net_sched: sch_fq: enable use of hrtimer slack

2020-03-18T04:16:35+00:00

Add a new attribute to control the fq qdisc hrtimer slack. Default is set to 10 usec. When/if packets are throttled, fq set up an hrtimer that can lead to one interrupt per packet in the throttled queue. By using a timer slack, we allow better use of timer interrupts, by giving them a chance to call multiple timer callbacks at each hardware interrupt. Also, giving a slack allows FQ to dequeue batches of packets instead of a single one, thus increasing xmit_more efficiency. This has no negative effect on the rate a TCP flow can sustain, since each TCP flow maintains its own precise vtime (tp->tcp_wstamp_ns) v2: added strict netlink checking (as feedback from Jakub Kicinski) Tested: 1000 concurrent flows all using paced packets. 1,000,000 packets sent per second. Before the patch : $ vmstat 2 10 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 0 60726784 23628 3485992 0 0 138 1 977 535 0 12 87 0 0 0 0 0 60714700 23628 3485628 0 0 0 0 1568827 26462 0 22 78 0 0 1 0 0 60716012 23628 3485656 0 0 0 0 1570034 26216 0 22 78 0 0 0 0 0 60722420 23628 3485492 0 0 0 0 1567230 26424 0 22 78 0 0 0 0 0 60727484 23628 3485556 0 0 0 0 1568220 26200 0 22 78 0 0 2 0 0 60718900 23628 3485380 0 0 0 40 1564721 26630 0 22 78 0 0 2 0 0 60718096 23628 3485332 0 0 0 0 1562593 26432 0 22 78 0 0 0 0 0 60719608 23628 3485064 0 0 0 0 1563806 26238 0 22 78 0 0 1 0 0 60722876 23628 3485236 0 0 0 130 1565874 26566 0 22 78 0 0 1 0 0 60722752 23628 3484908 0 0 0 0 1567646 26247 0 22 78 0 0 After the patch, slack of 10 usec, we can see a reduction of interrupts per second, and a small decrease of reported cpu usage. $ vmstat 2 10 procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 60722564 23628 3484728 0 0 133 1 696 545 0 13 87 0 0 1 0 0 60722568 23628 3484824 0 0 0 0 977278 25469 0 20 80 0 0 0 0 0 60716396 23628 3484764 0 0 0 0 979997 25326 0 20 80 0 0 0 0 0 60713844 23628 3484960 0 0 0 0 981394 25249 0 20 80 0 0 2 0 0 60720468 23628 3484916 0 0 0 0 982860 25062 0 20 80 0 0 1 0 0 60721236 23628 3484856 0 0 0 0 982867 25100 0 20 80 0 0 1 0 0 60722400 23628 3484456 0 0 0 8 982698 25303 0 20 80 0 0 0 0 0 60715396 23628 3484428 0 0 0 0 981777 25176 0 20 80 0 0 0 0 0 60716520 23628 3486544 0 0 0 36 978965 27857 0 21 79 0 0 0 0 0 60719592 23628 3486516 0 0 0 22 977318 25106 0 20 80 0 0 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

net: sched: RED: Introduce an ECN nodrop mode

2020-03-15T04:03:46+00:00

When the RED Qdisc is currently configured to enable ECN, the RED algorithm is used to decide whether a certain SKB should be marked. If that SKB is not ECN-capable, it is early-dropped. It is also possible to keep all traffic in the queue, and just mark the ECN-capable subset of it, as appropriate under the RED algorithm. Some switches support this mode, and some installations make use of it. To that end, add a new RED flag, TC_RED_NODROP. When the Qdisc is configured with this flag, non-ECT traffic is enqueued instead of being early-dropped. Signed-off-by: Petr Machata Reviewed-by: Jakub Kicinski Signed-off-by: David S. Miller