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2016-06-25net_sched: drop packets after root qdisc lock is releasedEric Dumazet1-3/+4
Qdisc performance suffers when packets are dropped at enqueue() time because drops (kfree_skb()) are done while qdisc lock is held, delaying a dequeue() draining the queue. Nominal throughput can be reduced by 50 % when this happens, at a time we would like the dequeue() to proceed as fast as possible. Even FQ is vulnerable to this problem, while one of FQ goals was to provide some flow isolation. This patch adds a 'struct sk_buff **to_free' parameter to all qdisc->enqueue(), and in qdisc_drop() helper. I measured a performance increase of up to 12 %, but this patch is a prereq so that future batches in enqueue() can fly. Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-15net_sched: sch_fq: defer skb freeingEric Dumazet1-6/+13
Both fq_change() and fq_reset() can use rtnl_kfree_skbs() Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-10net_sched: remove generic throttled managementEric Dumazet1-2/+1
__QDISC_STATE_THROTTLED bit manipulation is rather expensive for HTB and few others. I already removed it for sch_fq in commit f2600cf02b5b ("net: sched: avoid costly atomic operation in fq_dequeue()") and so far nobody complained. When one ore more packets are stuck in one or more throttled HTB class, a htb dequeue() performs two atomic operations to clear/set __QDISC_STATE_THROTTLED bit, while root qdisc lock is held. Removing this pair of atomic operations bring me a 8 % performance increase on 200 TCP_RR tests, in presence of throttled classes. This patch has no side effect, since nothing actually uses disc_is_throttled() anymore. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2016-02-29net_sched: update hierarchical backlog tooWANG Cong1-1/+3
When the bottom qdisc decides to, for example, drop some packet, it calls qdisc_tree_decrease_qlen() to update the queue length for all its ancestors, we need to update the backlog too to keep the stats on root qdisc accurate. Cc: Jamal Hadi Salim <jhs@mojatatu.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-11net: synack packets can be attached to request socketsEric Dumazet1-1/+2
selinux needs few changes to accommodate fact that SYNACK messages can be attached to a request socket, lacking sk_security pointer (Only syncookies are still attached to a TCP_LISTEN socket) Adds a new sk_listener() helper, and use it in selinux and sch_fq Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported by: kernel test robot <ying.huang@linux.intel.com> Cc: Paul Moore <paul@paul-moore.com> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: Eric Paris <eparis@parisplace.org> Acked-by: Paul Moore <paul@paul-moore.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-03tcp: attach SYNACK messages to request sockets instead of listenerEric Dumazet1-5/+7
If a listen backlog is very big (to avoid syncookies), then the listener sk->sk_wmem_alloc is the main source of false sharing, as we need to touch it twice per SYNACK re-transmit and TX completion. (One SYN packet takes listener lock once, but up to 6 SYNACK are generated) By attaching the skb to the request socket, we remove this source of contention. Tested: listen(fd, 10485760); // single listener (no SO_REUSEPORT) 16 RX/TX queue NIC Sustain a SYNFLOOD attack of ~320,000 SYN per second, Sending ~1,400,000 SYNACK per second. Perf profiles now show listener spinlock being next bottleneck. 20.29% [kernel] [k] queued_spin_lock_slowpath 10.06% [kernel] [k] __inet_lookup_established 5.12% [kernel] [k] reqsk_timer_handler 3.22% [kernel] [k] get_next_timer_interrupt 3.00% [kernel] [k] tcp_make_synack 2.77% [kernel] [k] ipt_do_table 2.70% [kernel] [k] run_timer_softirq 2.50% [kernel] [k] ip_finish_output 2.04% [kernel] [k] cascade Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-04-01pkt_sched: fq: correct spelling of locallySimon Horman1-2/+2
Correct spelling of locally. Also remove extra space before tab character in struct fq_flow. Signed-off-by: Simon Horman <simon.horman@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-02-05Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/netDavid S. Miller1-2/+8
Conflicts: drivers/net/vxlan.c drivers/vhost/net.c include/linux/if_vlan.h net/core/dev.c The net/core/dev.c conflict was the overlap of one commit marking an existing function static whilst another was adding a new function. In the include/linux/if_vlan.h case, the type used for a local variable was changed in 'net', whereas the function got rewritten to fix a stacked vlan bug in 'net-next'. In drivers/vhost/net.c, Al Viro's iov_iter conversions in 'net-next' overlapped with an endainness fix for VHOST 1.0 in 'net'. In drivers/net/vxlan.c, vxlan_find_vni() added a 'flags' parameter in 'net-next' whereas in 'net' there was a bug fix to pass in the correct network namespace pointer in calls to this function. Signed-off-by: David S. Miller <davem@davemloft.net>
2015-02-04pkt_sched: fq: better control of DDOS trafficEric Dumazet1-2/+17
FQ has a fast path for skb attached to a socket, as it does not have to compute a flow hash. But for other packets, FQ being non stochastic means that hosts exposed to random Internet traffic can allocate million of flows structure (104 bytes each) pretty easily. Not only host can OOM, but lookup in RB trees can take too much cpu and memory resources. This patch adds a new attribute, orphan_mask, that is adding possibility of having a stochastic hash for orphaned skb. Its default value is 1024 slots, to mimic SFQ behavior. Note: This does not apply to locally generated TCP traffic, and no locally generated traffic will share a flow structure with another perfect or stochastic flow. This patch also handles the specific case of SYNACK messages: They are attached to the listener socket, and therefore all map to a single hash bucket. If listener have set SO_MAX_PACING_RATE, hoping to have new accepted socket inherit this rate, SYNACK might be paced and even dropped. This is very similar to an internal patch Google have used more than one year. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-02-04tcp: do not pace pure ack packetsEric Dumazet1-2/+8
When we added pacing to TCP, we decided to let sch_fq take care of actual pacing. All TCP had to do was to compute sk->pacing_rate using simple formula: sk->pacing_rate = 2 * cwnd * mss / rtt It works well for senders (bulk flows), but not very well for receivers or even RPC : cwnd on the receiver can be less than 10, rtt can be around 100ms, so we can end up pacing ACK packets, slowing down the sender. Really, only the sender should pace, according to its own logic. Instead of adding a new bit in skb, or call yet another flow dissection, we tweak skb->truesize to a small value (2), and we instruct sch_fq to use new helper and not pace pure ack. Note this also helps TCP small queue, as ack packets present in qdisc/NIC do not prevent sending a data packet (RPC workload) This helps to reduce tx completion overhead, ack packets can use regular sock_wfree() instead of tcp_wfree() which is a bit more expensive. This has no impact in the case packets are sent to loopback interface, as we do not coalesce ack packets (were we would detect skb->truesize lie) In case netem (with a delay) is used, skb_orphan_partial() also sets skb->truesize to 1. This patch is a combination of two patches we used for about one year at Google. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-02-04pkt_sched: fq: avoid hang when quantum 0Kenneth Klette Jonassen1-2/+8
Configuring fq with quantum 0 hangs the system, presumably because of a non-interruptible infinite loop. Either way quantum 0 does not make sense. Reproduce with: sudo tc qdisc add dev lo root fq quantum 0 initial_quantum 0 ping 127.0.0.1 Signed-off-by: Kenneth Klette Jonassen <kennetkl@ifi.uio.no> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-28pkt_sched: fq: remove useless TIME_WAIT checkEric Dumazet1-2/+2
TIME_WAIT sockets are not owning any skb. ip_send_unicast_reply() and tcp_v6_send_response() both use regular sockets. We can safely remove a test in sch_fq and save one cache line miss, as sk_state is far away from sk_pacing_rate. Tested at Google for about one year. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-11-26pkt_sched: fq: increase max delay from 125 ms to one secondEric Dumazet1-5/+4
FQ/pacing has a clamp of delay of 125 ms, to avoid some possible harm. It turns out this delay is too small to allow pacing low rates : Some ISP setup very aggressive policers as low as 16kbit. Now TCP stack has spurious rtx prevention, it seems safe to increase this fixed parameter, without adding a qdisc attribute. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-10-06net: sched: avoid costly atomic operation in fq_dequeue()Eric Dumazet1-4/+2
Standard qdisc API to setup a timer implies an atomic operation on every packet dequeue : qdisc_unthrottled() It turns out this is not really needed for FQ, as FQ has no concept of global qdisc throttling, being a qdisc handling many different flows, some of them can be throttled, while others are not. Fix is straightforward : add a 'bool throttle' to qdisc_watchdog_schedule_ns(), and remove calls to qdisc_unthrottled() in sch_fq. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-30net: sched: implement qstat helper routinesJohn Fastabend1-2/+2
This adds helpers to manipulate qstats logic and replaces locations that touch the counters directly. This simplifies future patches to push qstats onto per cpu counters. Signed-off-by: John Fastabend <john.r.fastabend@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-08-22net: use ktime_get_ns() and ktime_get_real_ns() helpersEric Dumazet1-2/+2
ktime_get_ns() replaces ktime_to_ns(ktime_get()) ktime_get_real_ns() replaces ktime_to_ns(ktime_get_real()) Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-06-05net: use the new API kvfree()WANG Cong1-4/+1
It is available since v3.15-rc5. Cc: Pablo Neira Ayuso <pablo@netfilter.org> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-03-13net_sched: return nla_nest_end() instead of skb->lenYang Yingliang1-2/+1
nla_nest_end() already has return skb->len, so replace return skb->len with return nla_nest_end instead(). Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-03-08pkt_sched: fq: do not hold qdisc lock while allocating memoryEric Dumazet1-6/+15
Resizing fq hash table allocates memory while holding qdisc spinlock, with BH disabled. This is definitely not good, as allocation might sleep. We can drop the lock and get it when needed, we hold RTNL so no other changes can happen at the same time. Signed-off-by: Eric Dumazet <edumazet@google.com> Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler") Signed-off-by: David S. Miller <davem@davemloft.net>
2013-12-17net: Change skb_get_rxhash to skb_get_hashTom Herbert1-1/+1
Changing name of function as part of making the hash in skbuff to be generic property, not just for receive path. Signed-off-by: Tom Herbert <therbert@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-12-17pkt_sched: fq: more robust memory allocationEric Dumazet1-6/+28
This patch brings NUMA support and automatic fallback to vmalloc() in case kmalloc() failed to allocate FQ hash table. NUMA support depends on XPS being setup for the device before qdisc allocation. After a XPS change, it might be worth creating qdisc hierarchy again. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-11-15pkt_sched: fq: fix pacing for small framesEric Dumazet1-4/+18
For performance reasons, sch_fq tried hard to not setup timers for every sent packet, using a quantum based heuristic : A delay is setup only if the flow exhausted its credit. Problem is that application limited flows can refill their credit for every queued packet, and they can evade pacing. This problem can also be triggered when TCP flows use small MSS values, as TSO auto sizing builds packets that are smaller than the default fq quantum (3028 bytes) This patch adds a 40 ms delay to guard flow credit refill. Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Maciej Żenczykowski <maze@google.com> Cc: Willem de Bruijn <willemb@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-11-15pkt_sched: fq: warn users using defrateEric Dumazet1-6/+4
Commit 7eec4174ff29 ("pkt_sched: fq: fix non TCP flows pacing") obsoleted TCA_FQ_FLOW_DEFAULT_RATE without notice for the users. Suggested by David Miller Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-11-14pkt_sched: fq: change classification of control packetsMaciej Żenczykowski1-7/+1
Initial sch_fq implementation copied code from pfifo_fast to classify a packet as a high prio packet. This clashes with setups using PRIO with say 7 bands, as one of the band could be incorrectly (mis)classified by FQ. Packets would be queued in the 'internal' queue, and no pacing ever happen for this special queue. Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler") Signed-off-by: Maciej Żenczykowski <maze@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Willem de Bruijn <willemb@google.com> Cc: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-10-28pkt_sched: fq: clear time_next_packet for reused flowsEric Dumazet1-0/+1
When a socket is freed/reallocated, we need to clear time_next_packet or else we can inherit a prior value and delay first packets of the new flow. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-10-08pkt_sched: fq: fix non TCP flows pacingEric Dumazet1-11/+9
Steinar reported FQ pacing was not working for UDP flows. It looks like the initial sk->sk_pacing_rate value of 0 was a wrong choice. We should init it to ~0U (unlimited) Then, TCA_FQ_FLOW_DEFAULT_RATE should be removed because it makes no real sense. The default rate is really unlimited, and we need to avoid a zero divide. Reported-by: Steinar H. Gunderson <sesse@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-10-08pkt_sched: fq: fix typo for initial_quantumEric Dumazet1-1/+1
TCA_FQ_INITIAL_QUANTUM should set q->initial_quantum Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-10-01pkt_sched: fq: rate limiting improvementsEric Dumazet1-19/+26
FQ rate limiting suffers from two problems, reported by Steinar : 1) FQ enforces a delay when flow quantum is exhausted in order to reduce cpu overhead. But if packets are small, current delay computation is slightly wrong, and observed rates can be too high. Steinar had this problem because he disabled TSO and GSO, and default FQ quantum is 2*1514. (Of course, I wish recent TSO auto sizing changes will help to not having to disable TSO in the first place) 2) maxrate was not used for forwarded flows (skbs not attached to a socket) Tested: tc qdisc add dev eth0 root est 1sec 4sec fq maxrate 8Mbit netperf -H lpq84 -l 1000 & sleep 10 ; tc -s qdisc show dev eth0 qdisc fq 8003: root refcnt 32 limit 10000p flow_limit 100p buckets 1024 quantum 3028 initial_quantum 15140 maxrate 8000Kbit Sent 16819357 bytes 11258 pkt (dropped 0, overlimits 0 requeues 0) rate 7831Kbit 653pps backlog 7570b 5p requeues 0 44 flows (43 inactive, 1 throttled), next packet delay 2977352 ns 0 gc, 0 highprio, 5545 throttled lpq83:~# tcpdump -p -i eth0 host lpq84 -c 12 09:02:52.079484 IP lpq83 > lpq84: . 1389536928:1389538376(1448) ack 3808678021 win 457 <nop,nop,timestamp 961812 572609068> 09:02:52.079499 IP lpq83 > lpq84: . 1448:2896(1448) ack 1 win 457 <nop,nop,timestamp 961812 572609068> 09:02:52.079906 IP lpq84 > lpq83: . ack 2896 win 16384 <nop,nop,timestamp 572609080 961812> 09:02:52.082568 IP lpq83 > lpq84: . 2896:4344(1448) ack 1 win 457 <nop,nop,timestamp 961815 572609071> 09:02:52.082581 IP lpq83 > lpq84: . 4344:5792(1448) ack 1 win 457 <nop,nop,timestamp 961815 572609071> 09:02:52.083017 IP lpq84 > lpq83: . ack 5792 win 16384 <nop,nop,timestamp 572609083 961815> 09:02:52.085678 IP lpq83 > lpq84: . 5792:7240(1448) ack 1 win 457 <nop,nop,timestamp 961818 572609074> 09:02:52.085693 IP lpq83 > lpq84: . 7240:8688(1448) ack 1 win 457 <nop,nop,timestamp 961818 572609074> 09:02:52.086117 IP lpq84 > lpq83: . ack 8688 win 16384 <nop,nop,timestamp 572609086 961818> 09:02:52.088792 IP lpq83 > lpq84: . 8688:10136(1448) ack 1 win 457 <nop,nop,timestamp 961821 572609077> 09:02:52.088806 IP lpq83 > lpq84: . 10136:11584(1448) ack 1 win 457 <nop,nop,timestamp 961821 572609077> 09:02:52.089217 IP lpq84 > lpq83: . ack 11584 win 16384 <nop,nop,timestamp 572609090 961821> Reported-by: Steinar H. Gunderson <sesse@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-09-30pkt_sched: fq: qdisc dismantle fixesEric Dumazet1-20/+37
fq_reset() should drops all packets in queue, including throttled flows. This patch moves code from fq_destroy() to fq_reset() to do the cleaning. fq_change() must stop calling fq_dequeue() if all remaining packets are from throttled flows. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-08-30pkt_sched: fq: prefetch() fixEric Dumazet1-1/+2
kbuild bot reported following m68k build error : net/sched/sch_fq.c: In function 'fq_dequeue': >> net/sched/sch_fq.c:491:2: error: implicit declaration of function 'prefetch' [-Werror=implicit-function-declaration] cc1: some warnings being treated as errors While we are fixing this, move this prefetch() call a bit earlier. Reported-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-08-29pkt_sched: fq: Fair Queue packet schedulerEric Dumazet1-0/+792
- Uses perfect flow match (not stochastic hash like SFQ/FQ_codel) - Uses the new_flow/old_flow separation from FQ_codel - New flows get an initial credit allowing IW10 without added delay. - Special FIFO queue for high prio packets (no need for PRIO + FQ) - Uses a hash table of RB trees to locate the flows at enqueue() time - Smart on demand gc (at enqueue() time, RB tree lookup evicts old unused flows) - Dynamic memory allocations. - Designed to allow millions of concurrent flows per Qdisc. - Small memory footprint : ~8K per Qdisc, and 104 bytes per flow. - Single high resolution timer for throttled flows (if any). - One RB tree to link throttled flows. - Ability to have a max rate per flow. We might add a socket option to add per socket limitation. Attempts have been made to add TCP pacing in TCP stack, but this seems to add complex code to an already complex stack. TCP pacing is welcomed for flows having idle times, as the cwnd permits TCP stack to queue a possibly large number of packets. This removes the 'slow start after idle' choice, hitting badly large BDP flows, and applications delivering chunks of data as video streams. Nicely spaced packets : Here interface is 10Gbit, but flow bottleneck is ~20Mbit cwin is big, yet FQ avoids the typical bursts generated by TCP (as in netperf TCP_RR -- -r 100000,100000) 15:01:23.545279 IP A > B: . 78193:81089(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.545394 IP B > A: . ack 81089 win 3668 <nop,nop,timestamp 11597985 1115> 15:01:23.546488 IP A > B: . 81089:83985(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.546565 IP B > A: . ack 83985 win 3668 <nop,nop,timestamp 11597986 1115> 15:01:23.547713 IP A > B: . 83985:86881(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.547778 IP B > A: . ack 86881 win 3668 <nop,nop,timestamp 11597987 1115> 15:01:23.548911 IP A > B: . 86881:89777(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.548949 IP B > A: . ack 89777 win 3668 <nop,nop,timestamp 11597988 1115> 15:01:23.550116 IP A > B: . 89777:92673(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.550182 IP B > A: . ack 92673 win 3668 <nop,nop,timestamp 11597989 1115> 15:01:23.551333 IP A > B: . 92673:95569(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.551406 IP B > A: . ack 95569 win 3668 <nop,nop,timestamp 11597991 1115> 15:01:23.552539 IP A > B: . 95569:98465(2896) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.552576 IP B > A: . ack 98465 win 3668 <nop,nop,timestamp 11597992 1115> 15:01:23.553756 IP A > B: . 98465:99913(1448) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.554138 IP A > B: P 99913:100001(88) ack 65248 win 3125 <nop,nop,timestamp 1115 11597805> 15:01:23.554204 IP B > A: . ack 100001 win 3668 <nop,nop,timestamp 11597993 1115> 15:01:23.554234 IP B > A: . 65248:68144(2896) ack 100001 win 3668 <nop,nop,timestamp 11597993 1115> 15:01:23.555620 IP B > A: . 68144:71040(2896) ack 100001 win 3668 <nop,nop,timestamp 11597993 1115> 15:01:23.557005 IP B > A: . 71040:73936(2896) ack 100001 win 3668 <nop,nop,timestamp 11597993 1115> 15:01:23.558390 IP B > A: . 73936:76832(2896) ack 100001 win 3668 <nop,nop,timestamp 11597993 1115> 15:01:23.559773 IP B > A: . 76832:79728(2896) ack 100001 win 3668 <nop,nop,timestamp 11597993 1115> 15:01:23.561158 IP B > A: . 79728:82624(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.562543 IP B > A: . 82624:85520(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.563928 IP B > A: . 85520:88416(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.565313 IP B > A: . 88416:91312(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.566698 IP B > A: . 91312:94208(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.568083 IP B > A: . 94208:97104(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.569467 IP B > A: . 97104:100000(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.570852 IP B > A: . 100000:102896(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.572237 IP B > A: . 102896:105792(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.573639 IP B > A: . 105792:108688(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.575024 IP B > A: . 108688:111584(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.576408 IP B > A: . 111584:114480(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> 15:01:23.577793 IP B > A: . 114480:117376(2896) ack 100001 win 3668 <nop,nop,timestamp 11597994 1115> TCP timestamps show that most packets from B were queued in the same ms timeframe (TSval 1159799{3,4}), but FQ managed to send them right in time to avoid a big burst. In slow start or steady state, very few packets are throttled [1] FQ gets a bunch of tunables as : limit : max number of packets on whole Qdisc (default 10000) flow_limit : max number of packets per flow (default 100) quantum : the credit per RR round (default is 2 MTU) initial_quantum : initial credit for new flows (default is 10 MTU) maxrate : max per flow rate (default : unlimited) buckets : number of RB trees (default : 1024) in hash table. (consumes 8 bytes per bucket) [no]pacing : disable/enable pacing (default is enable) All of them can be changed on a live qdisc. $ tc qd add dev eth0 root fq help Usage: ... fq [ limit PACKETS ] [ flow_limit PACKETS ] [ quantum BYTES ] [ initial_quantum BYTES ] [ maxrate RATE ] [ buckets NUMBER ] [ [no]pacing ] $ tc -s -d qd qdisc fq 8002: dev eth0 root refcnt 32 limit 10000p flow_limit 100p buckets 256 quantum 3028 initial_quantum 15140 Sent 216532416 bytes 148395 pkt (dropped 0, overlimits 0 requeues 14) backlog 0b 0p requeues 14 511 flows, 511 inactive, 0 throttled 110 gc, 0 highprio, 0 retrans, 1143 throttled, 0 flows_plimit [1] Except if initial srtt is overestimated, as if using cached srtt in tcp metrics. We'll provide a fix for this issue. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-23 14:26:30 +0000