[Bloat] Excessive throttling with fq
Eric Dumazet
eric.dumazet at gmail.com
Thu Jan 26 16:00:52 EST 2017
For some reason, even though this NIC advertises TSO support,
tcpdump clearly shows TSO is not used at all.
Oh wait, maybe TSO is not enabled on the bonding device ?
On Thu, 2017-01-26 at 21:46 +0100, Hans-Kristian Bakke wrote:
> # ethtool -i eth0
> driver: e1000e
> version: 3.2.6-k
> firmware-version: 1.9-0
> expansion-rom-version:
> bus-info: 0000:04:00.0
> supports-statistics: yes
> supports-test: yes
> supports-eeprom-access: yes
> supports-register-dump: yes
> supports-priv-flags: no
>
>
> # ethtool -k eth0
> Features for eth0:
> rx-checksumming: on
> tx-checksumming: on
> tx-checksum-ipv4: off [fixed]
> tx-checksum-ip-generic: on
> tx-checksum-ipv6: off [fixed]
> tx-checksum-fcoe-crc: off [fixed]
> tx-checksum-sctp: off [fixed]
> scatter-gather: on
> tx-scatter-gather: on
> tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: on
> tx-tcp-segmentation: on
> tx-tcp-ecn-segmentation: off [fixed]
> tx-tcp-mangleid-segmentation: on
> tx-tcp6-segmentation: on
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: on
> generic-receive-offload: on
> large-receive-offload: off [fixed]
> rx-vlan-offload: on
> tx-vlan-offload: on
> ntuple-filters: off [fixed]
> receive-hashing: on
> highdma: on [fixed]
> rx-vlan-filter: on [fixed]
> vlan-challenged: off [fixed]
> tx-lockless: off [fixed]
> netns-local: off [fixed]
> tx-gso-robust: off [fixed]
> tx-fcoe-segmentation: off [fixed]
> tx-gre-segmentation: off [fixed]
> tx-gre-csum-segmentation: off [fixed]
> tx-ipxip4-segmentation: off [fixed]
> tx-ipxip6-segmentation: off [fixed]
> tx-udp_tnl-segmentation: off [fixed]
> tx-udp_tnl-csum-segmentation: off [fixed]
> tx-gso-partial: off [fixed]
> tx-sctp-segmentation: off [fixed]
> fcoe-mtu: off [fixed]
> tx-nocache-copy: off
> loopback: off [fixed]
> rx-fcs: off
> rx-all: off
> tx-vlan-stag-hw-insert: off [fixed]
> rx-vlan-stag-hw-parse: off [fixed]
> rx-vlan-stag-filter: off [fixed]
> l2-fwd-offload: off [fixed]
> busy-poll: off [fixed]
> hw-tc-offload: off [fixed]
>
>
> # grep HZ /boot/config-4.8.0-2-amd64
> CONFIG_NO_HZ_COMMON=y
> # CONFIG_HZ_PERIODIC is not set
> CONFIG_NO_HZ_IDLE=y
> # CONFIG_NO_HZ_FULL is not set
> # CONFIG_NO_HZ is not set
> # CONFIG_HZ_100 is not set
> CONFIG_HZ_250=y
> # CONFIG_HZ_300 is not set
> # CONFIG_HZ_1000 is not set
> CONFIG_HZ=250
> CONFIG_MACHZ_WDT=m
>
>
>
> On 26 January 2017 at 21:41, Eric Dumazet <eric.dumazet at gmail.com>
> wrote:
>
> Can you post :
>
> ethtool -i eth0
> ethtool -k eth0
>
> grep HZ /boot/config.... (what is the HZ value of your kernel)
>
> I suspect a possible problem with TSO autodefer when/if HZ <
> 1000
>
> Thanks.
>
> On Thu, 2017-01-26 at 21:19 +0100, Hans-Kristian Bakke wrote:
> > There are two packet captures from fq with and without
> pacing here:
> >
> >
> > https://owncloud.proikt.com/index.php/s/KuXIl8h8bSFH1fM
> >
> >
> >
> > The server (with fq pacing/nopacing) is 10.0.5.10 and is
> running a
> > Apache2 webserver at port tcp port 443. The tcp client is
> nginx
> > reverse proxy at 10.0.5.13 on the same subnet which again is
> proxying
> > the connection from the Windows 10 client.
> > - I did try to connect directly to the server with the
> client (via a
> > linux gateway router) avoiding the nginx proxy and just
> using plain
> > no-ssl http. That did not change anything.
> > - I also tried stopping the eth0 interface to force the
> traffic to the
> > eth1 interface in the LACP which changed nothing.
> > - I also pulled each of the cable on the switch to force the
> traffic
> > to switch between interfaces in the LACP link between the
> client
> > switch and the server switch.
> >
> >
> > The CPU is a 5-6 year old Intel Xeon X3430 CPU @ 4x2.40GHz
> on a
> > SuperMicro platform. It is not very loaded and the results
> are always
> > in the same ballpark with fq pacing on.
> >
> >
> >
> > top - 21:12:38 up 12 days, 11:08, 4 users, load average:
> 0.56, 0.68,
> > 0.77
> > Tasks: 1344 total, 1 running, 1343 sleeping, 0
> stopped, 0 zombie
> > %Cpu0 : 0.0 us, 1.0 sy, 0.0 ni, 99.0 id, 0.0 wa, 0.0
> hi, 0.0
> > si, 0.0 st
> > %Cpu1 : 0.0 us, 0.3 sy, 0.0 ni, 97.4 id, 2.0 wa, 0.0
> hi, 0.3
> > si, 0.0 st
> > %Cpu2 : 0.0 us, 2.0 sy, 0.0 ni, 96.4 id, 1.3 wa, 0.0
> hi, 0.3
> > si, 0.0 st
> > %Cpu3 : 0.7 us, 2.3 sy, 0.0 ni, 94.1 id, 3.0 wa, 0.0
> hi, 0.0
> > si, 0.0 st
> > KiB Mem : 16427572 total, 173712 free, 9739976 used,
> 6513884
> > buff/cache
> > KiB Swap: 6369276 total, 6126736 free, 242540 used.
> 6224836 avail
> > Mem
> >
> >
> > This seems OK to me. It does have 24 drives in 3 ZFS pools
> at 144TB
> > raw storage in total with several SAS HBAs that is pretty
> much always
> > poking the system in some way or the other.
> >
> >
> > There are around 32K interrupts when running @23 MB/s (as
> seen in
> > chrome downloads) with pacing on and about 25K interrupts
> when running
> > @105 MB/s with fq nopacing. Is that normal?
> >
> >
> > Hans-Kristian
> >
> >
> >
> > On 26 January 2017 at 20:58, David Lang <david at lang.hm>
> wrote:
> > Is there any CPU bottleneck?
> >
> > pacing causing this sort of problem makes me thing
> that the
> > CPU either can't keep up or that something (Hz
> setting type of
> > thing) is delaying when the CPU can get used.
> >
> > It's not clear from the posts if the problem is with
> sending
> > data or receiving data.
> >
> > David Lang
> >
> >
> > On Thu, 26 Jan 2017, Eric Dumazet wrote:
> >
> > Nothing jumps on my head.
> >
> > We use FQ on links varying from 1Gbit to
> 100Gbit, and
> > we have no such
> > issues.
> >
> > You could probably check on the server the
> TCP various
> > infos given by ss
> > command
> >
> >
> > ss -temoi dst <remoteip>
> >
> >
> > pacing rate is shown. You might have some
> issues, but
> > it is hard to say.
> >
> >
> > On Thu, 2017-01-26 at 19:55 +0100,
> Hans-Kristian Bakke
> > wrote:
> > After some more testing I see that
> if I
> > disable fq pacing the
> > performance is restored to the
> expected
> > levels: # for i in eth0 eth1; do tc
> qdisc
> > replace dev $i root fq nopacing;
> > done
> >
> >
> > Is this expected behaviour? There is
> some
> > background traffic, but only
> > in the sub 100 mbit/s on the
> switches and
> > gateway between the server
> > and client.
> >
> >
> > The chain:
> > Windows 10 client -> 1000 mbit/s ->
> switch ->
> > 2xgigabit LACP -> switch
> > -> 4 x gigabit LACP -> gw (fq_codel
> on all
> > nics) -> 4 x gigabit LACP
> > (the same as in) -> switch -> 2 x
> lacp ->
> > server (with misbehaving fq
> > pacing)
> >
> >
> >
> > On 26 January 2017 at 19:38,
> Hans-Kristian
> > Bakke <hkbakke at gmail.com>
> > wrote:
> > I can add that this is
> without BBR,
> > just plain old kernel 4.8
> > cubic.
> >
> > On 26 January 2017 at 19:36,
> > Hans-Kristian Bakke
> > <hkbakke at gmail.com> wrote:
> > Another day, another
> fq issue
> > (or user error).
> >
> >
> > I try to do the
> seeminlig
> > simple task of downloading a
> > single large file
> over local
> > gigabit LAN from a
> > physical server
> running kernel
> > 4.8 and sch_fq on intel
> > server NICs.
> >
> >
> > For some reason it
> wouldn't go
> > past around 25 MB/s.
> > After having
> replaced SSL with
> > no SSL, replaced apache
> > with nginx and
> verified that
> > there is plenty of
> > bandwith available
> between my
> > client and the server I
> > tried to change
> qdisc from fq
> > to pfifo_fast. It
> > instantly shot up to
> around
> > the expected 85-90 MB/s.
> > The same happened
> with
> > fq_codel in place of fq.
> >
> >
> > I then checked the
> statistics
> > for fq and the throttled
> > counter is
> increasing
> > massively every second (eth0 and
> > eth1 is LACPed using
> Linux
> > bonding so both is seen
> > here):
> >
> >
> > qdisc fq 8007: root
> refcnt 2
> > limit 10000p flow_limit
> > 100p buckets 1024
> orphan_mask
> > 1023 quantum 3028
> > initial_quantum
> 15140
> > refill_delay 40.0ms
> > Sent 787131797
> bytes 520082
> > pkt (dropped 15,
> > overlimits 0
> requeues 0)
> > backlog 98410b 65p
> requeues 0
> > 15 flows (14
> inactive, 1
> > throttled)
> > 0 gc, 2 highprio,
> 259920
> > throttled, 15 flows_plimit
> > qdisc fq 8008: root
> refcnt 2
> > limit 10000p flow_limit
> > 100p buckets 1024
> orphan_mask
> > 1023 quantum 3028
> > initial_quantum
> 15140
> > refill_delay 40.0ms
> > Sent 2533167 bytes
> 6731 pkt
> > (dropped 0, overlimits 0
> > requeues 0)
> > backlog 0b 0p
> requeues 0
> > 24 flows (24
> inactive, 0
> > throttled)
> > 0 gc, 2 highprio,
> 397
> > throttled
> >
> >
> > Do you have any
> suggestions?
> >
> >
> > Regards,
> > Hans-Kristian
> >
> >
> >
> >
> >
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