On small embedded routers, one wants to control maximal amount of
memory used by fq_codel, instead of controlling number of packets or
bytes, since GRO/TSO make these not practical.
Assuming skb->truesize is accurate, we have to keep track of
skb->truesize sum for skbs in queue.
This patch adds a new TCA_FQ_CODEL_MEMORY_LIMIT attribute.
I chose a default value of 32 MBytes, which looks reasonable even
for heavy duty usages. (Prior fq_codel users should not be hurt
when they upgrade their kernels)
Two fields are added to tc_fq_codel_qd_stats to report :
- Current memory usage
- Number of drops caused by memory limits
# tc qd replace dev eth1 root est 1sec 4sec fq_codel memory_limit 4M
..
# tc -s -d qd sh dev eth1
qdisc fq_codel 8008: root refcnt 257 limit 10240p flows 1024
quantum 1514 target 5.0ms interval 100.0ms memory_limit 4Mb ecn
Sent 2083566791363 bytes 1376214889 pkt (dropped 4994406, overlimits 0
requeues 21705223)
rate 9841Mbit 812549pps backlog 3906120b 376p requeues 21705223
maxpacket 68130 drop_overlimit 4994406 new_flow_count 28855414
ecn_mark 0 memory_used 4190048 drop_overmemory 4994406
new_flows_len 1 old_flows_len 177
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Dave Täht <dave.taht@gmail.com>
Cc: Sebastian Möller <moeller0@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
In presence of inelastic flows and stress, we can call
fq_codel_drop() for every packet entering fq_codel qdisc.
fq_codel_drop() is quite expensive, as it does a linear scan
of 4 KB of memory to find a fat flow.
Once found, it drops the oldest packet of this flow.
Instead of dropping a single packet, try to drop 50% of the backlog
of this fat flow, with a configurable limit of 64 packets per round.
TCA_FQ_CODEL_DROP_BATCH_SIZE is the new attribute to make this
limit configurable.
With this strategy the 4 KB search is amortized to a single cache line
per drop [1], so fq_codel_drop() no longer appears at the top of kernel
profile in presence of few inelastic flows.
[1] Assuming a 64byte cache line, and 1024 buckets
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dave Taht <dave.taht@gmail.com>
Cc: Jonathan Morton <chromatix99@gmail.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Dave Taht
Signed-off-by: David S. Miller <davem@davemloft.net>
It was impossible to include codel.h for the
purpose of having access to codel_params or
codel_vars structure definitions and using them
for embedding in other more complex structures.
This splits allows codel.h itself to be treated
like any other header file while codel_qdisc.h and
codel_impl.h contain function definitions with
logic that was previously in codel.h.
This copies over copyrights and doesn't involve
code changes other than adding a few additional
include directives to net/sched/sch*codel.c.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This strips out qdisc specific bits from the code
and makes it slightly more reusable. Codel will be
used by wireless/mac80211 in the future.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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>
For classifiers getting invoked via tc_classify(), we always need an
extra function call into tc_classify_compat(), as both are being
exported as symbols and tc_classify() itself doesn't do much except
handling of reclassifications when tp->classify() returned with
TC_ACT_RECLASSIFY.
CBQ and ATM are the only qdiscs that directly call into tc_classify_compat(),
all others use tc_classify(). When tc actions are being configured
out in the kernel, tc_classify() effectively does nothing besides
delegating.
We could spare this layer and consolidate both functions. pktgen on
single CPU constantly pushing skbs directly into the netif_receive_skb()
path with a dummy classifier on ingress qdisc attached, improves
slightly from 22.3Mpps to 23.1Mpps.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Alex reported the following crash when using fq_codel
with htb:
crash> bt
PID: 630839 TASK: ffff8823c990d280 CPU: 14 COMMAND: "tc"
[... snip ...]
#8 [ffff8820ceec17a0] page_fault at ffffffff8160a8c2
[exception RIP: htb_qlen_notify+24]
RIP: ffffffffa0841718 RSP: ffff8820ceec1858 RFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88241747b400
RDX: ffff88241747b408 RSI: 0000000000000000 RDI: ffff8811fb27d000
RBP: ffff8820ceec1868 R8: ffff88120cdeff24 R9: ffff88120cdeff30
R10: 0000000000000bd4 R11: ffffffffa0840919 R12: ffffffffa0843340
R13: 0000000000000000 R14: 0000000000000001 R15: ffff8808dae5c2e8
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#9 [...] qdisc_tree_decrease_qlen at ffffffff81565375
#10 [...] fq_codel_dequeue at ffffffffa084e0a0 [sch_fq_codel]
#11 [...] fq_codel_reset at ffffffffa084e2f8 [sch_fq_codel]
#12 [...] qdisc_destroy at ffffffff81560d2d
#13 [...] htb_destroy_class at ffffffffa08408f8 [sch_htb]
#14 [...] htb_put at ffffffffa084095c [sch_htb]
#15 [...] tc_ctl_tclass at ffffffff815645a3
#16 [...] rtnetlink_rcv_msg at ffffffff81552cb0
[... snip ...]
As Jamal pointed out, there is actually no need to call dequeue
to purge the queued skb's in reset, data structures can be just
reset explicitly. Therefore, we reset everything except config's
and stats, so that we would have a fresh start after device flipping.
Fixes: 4b549a2ef4 ("fq_codel: Fair Queue Codel AQM")
Reported-by: Alex Gartrell <agartrell@fb.com>
Cc: Alex Gartrell <agartrell@fb.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
[xiyou.wangcong@gmail.com: added codel_vars_init() and qdisc_qstats_backlog_dec()]
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The ->drop() is supposed to return the number of bytes it dropped,
however fq_codel_drop() returns the index of the flow where it drops
a packet from.
Fix this by introducing a helper to wrap fq_codel_drop().
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fixes: 25331d6ce4 ("net: sched: implement qstat helper routines")
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Four minor merge conflicts:
1) qca_spi.c renamed the local variable used for the SPI device
from spi_device to spi, meanwhile the spi_set_drvdata() call
got moved further up in the probe function.
2) Two changes were both adding new members to codel params
structure, and thus we had overlapping changes to the
initializer function.
3) 'net' was making a fix to sk_release_kernel() which is
completely removed in 'net-next'.
4) In net_namespace.c, the rtnl_net_fill() call for GET operations
had the command value fixed, meanwhile 'net-next' adjusted the
argument signature a bit.
This also matches example merge resolutions posted by Stephen
Rothwell over the past two days.
Signed-off-by: David S. Miller <davem@davemloft.net>
For DCTCP or similar ECN based deployments on fabrics with shallow
buffers, hosts are responsible for a good part of the buffering.
This patch adds an optional ce_threshold to codel & fq_codel qdiscs,
so that DCTCP can have feedback from queuing in the host.
A DCTCP enabled egress port simply have a queue occupancy threshold
above which ECT packets get CE mark.
In codel language this translates to a sojourn time, so that one doesn't
have to worry about bytes or bandwidth but delays.
This makes the host an active participant in the health of the whole
network.
This also helps experimenting DCTCP in a setup without DCTCP compliant
fabric.
On following example, ce_threshold is set to 1ms, and we can see from
'ldelay xxx us' that TCP is not trying to go around the 5ms codel
target.
Queue has more capacity to absorb inelastic bursts (say from UDP
traffic), as queues are maintained to an optimal level.
lpaa23:~# ./tc -s -d qd sh dev eth1
qdisc mq 1: dev eth1 root
Sent 87910654696 bytes 58065331 pkt (dropped 0, overlimits 0 requeues 42961)
backlog 3108242b 364p requeues 42961
qdisc codel 8063: dev eth1 parent 1:1 limit 1000p target 5.0ms ce_threshold 1.0ms interval 100.0ms
Sent 7363778701 bytes 4863809 pkt (dropped 0, overlimits 0 requeues 5503)
rate 2348Mbit 193919pps backlog 255866b 46p requeues 5503
count 0 lastcount 0 ldelay 1.0ms drop_next 0us
maxpacket 68130 ecn_mark 0 drop_overlimit 0 ce_mark 72384
qdisc codel 8064: dev eth1 parent 1:2 limit 1000p target 5.0ms ce_threshold 1.0ms interval 100.0ms
Sent 7636486190 bytes 5043942 pkt (dropped 0, overlimits 0 requeues 5186)
rate 2319Mbit 191538pps backlog 207418b 64p requeues 5186
count 0 lastcount 0 ldelay 694us drop_next 0us
maxpacket 68130 ecn_mark 0 drop_overlimit 0 ce_mark 69873
qdisc codel 8065: dev eth1 parent 1:3 limit 1000p target 5.0ms ce_threshold 1.0ms interval 100.0ms
Sent 11569360142 bytes 7641602 pkt (dropped 0, overlimits 0 requeues 5554)
rate 3041Mbit 251096pps backlog 210446b 59p requeues 5554
count 0 lastcount 0 ldelay 889us drop_next 0us
maxpacket 68130 ecn_mark 0 drop_overlimit 0 ce_mark 37780
...
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Glenn Judd <glenn.judd@morganstanley.com>
Cc: Nandita Dukkipati <nanditad@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Call skb_get_hash_perturb instead of doing skb_flow_dissect and then
jhash by hand.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Under presence of TSO/GSO/GRO packets, codel at low rates can be quite
useless. In following example, not a single packet was ever dropped,
while average delay in codel queue is ~100 ms !
qdisc codel 0: parent 1:12 limit 16000p target 5.0ms interval 100.0ms
Sent 134376498 bytes 88797 pkt (dropped 0, overlimits 0 requeues 0)
backlog 13626b 3p requeues 0
count 0 lastcount 0 ldelay 96.9ms drop_next 0us
maxpacket 9084 ecn_mark 0 drop_overlimit 0
This comes from a confusion of what should be the minimal backlog. It is
pretty clear it is not 64KB or whatever max GSO packet ever reached the
qdisc.
codel intent was to use MTU of the device.
After the fix, we finally drop some packets, and rtt/cwnd of my single
TCP flow are meeting our expectations.
qdisc codel 0: parent 1:12 limit 16000p target 5.0ms interval 100.0ms
Sent 102798497 bytes 67912 pkt (dropped 1365, overlimits 0 requeues 0)
backlog 6056b 3p requeues 0
count 1 lastcount 1 ldelay 36.3ms drop_next 0us
maxpacket 10598 ecn_mark 0 drop_overlimit 0
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Kathleen Nichols <nichols@pollere.com>
Cc: Dave Taht <dave.taht@gmail.com>
Cc: Van Jacobson <vanj@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
commit 46e5da40ae (net: qdisc: use rcu prefix and silence
sparse warnings) triggers a spurious warning:
net/sched/sch_fq_codel.c:97 suspicious rcu_dereference_check() usage!
The code should be using the _bh variant of rcu_dereference.
Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
After previous patches to simplify qstats the qstats can be
made per cpu with a packed union in Qdisc struct.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This removes the use of qstats->qlen variable from the classifiers
and makes it an explicit argument to gnet_stats_copy_queue().
The qlen represents the qdisc queue length and is packed into
the qstats at the last moment before passnig to user space. By
handling it explicitely we avoid, in the percpu stats case, having
to figure out which per_cpu variable to put it in.
It would probably be best to remove it from qstats completely
but qstats is a user space ABI and can't be broken. A future
patch could make an internal only qstats structure that would
avoid having to allocate an additional u32 variable on the
Qdisc struct. This would make the qstats struct 128bits instead
of 128+32.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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>
rcu'ify tcf_proto this allows calling tc_classify() without holding
any locks. Updaters are protected by RTNL.
This patch prepares the core net_sched infrastracture for running
the classifier/action chains without holding the qdisc lock however
it does nothing to ensure cls_xxx and act_xxx types also work without
locking. Additional patches are required to address the fall out.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Replace open codings of (((u64) <x> * <y>) >> 32) with reciprocal_scale().
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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>
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>
This patch removes the net_random and net_srandom macros and replaces
them with direct calls to the prandom ones. As new commits only seem to
use prandom_u32 there is no use to keep them around.
This change makes it easier to grep for users of prandom_u32.
Signed-off-by: Aruna-Hewapathirane <aruna.hewapathirane@gmail.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently, we hold a max of sch->limit -1 number of packets instead of
sch->limit packets. Fix this off-by-one error.
Signed-off-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When fq_codel builds a new flow, it should not reset codel state.
Codel algo needs to get previous values (lastcount, drop_next) to get
proper behavior.
Signed-off-by: Dave Taht <dave.taht@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Dave Taht <dave.taht@bufferbloat.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
codel_should_drop() logic allows a packet being not dropped if queue
size is under max packet size.
In fq_codel, we have two possible backlogs : The qdisc global one, and
the flow local one.
The meaningful one for codel_should_drop() should be the global backlog,
not the per flow one, so that thin flows can have a non zero drop/mark
probability.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Dave Taht <dave.taht@bufferbloat.net>
Cc: Kathleen Nichols <nichols@pollere.com>
Cc: Van Jacobson <van@pollere.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix the following build error:
net/sched/sch_fq_codel.c: In function 'fq_codel_dump_stats':
net/sched/sch_fq_codel.c:464:3: error: unknown field 'qdisc_stats' specified in initializer
net/sched/sch_fq_codel.c:464:3: warning: missing braces around initializer
net/sched/sch_fq_codel.c:464:3: warning: (near initialization for 'st.<anonymous>')
net/sched/sch_fq_codel.c:465:3: error: unknown field 'qdisc_stats' specified in initializer
net/sched/sch_fq_codel.c:465:3: warning: excess elements in struct initializer
net/sched/sch_fq_codel.c:465:3: warning: (near initialization for 'st')
net/sched/sch_fq_codel.c:466:3: error: unknown field 'qdisc_stats' specified in initializer
net/sched/sch_fq_codel.c:466:3: warning: excess elements in struct initializer
net/sched/sch_fq_codel.c:466:3: warning: (near initialization for 'st')
net/sched/sch_fq_codel.c:467:3: error: unknown field 'qdisc_stats' specified in initializer
net/sched/sch_fq_codel.c:467:3: warning: excess elements in struct initializer
net/sched/sch_fq_codel.c:467:3: warning: (near initialization for 'st')
make[1]: *** [net/sched/sch_fq_codel.o] Error 1
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Eric Dumazet