netdev - Re: [RFC PATCH] ip: re-introduce fragments cache worker

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Message-ID: <83d36724c67d89f3cecec70f45179160653a2c01.camel@redhat.com>
Date:   Mon, 09 Jul 2018 11:43:37 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Westphal <fw@...len.de>, NeilBrown <neilb@...e.com>
Subject: Re: [RFC PATCH] ip: re-introduce fragments cache worker

On Fri, 2018-07-06 at 07:20 -0700, Eric Dumazet wrote:
> I will test/polish it later, I am coming back from vacations and have a backlog.
> 
> Here are my results : (Note that I have _not_ changed /proc/sys/net/ipv4/ipfrag_time )
> 
> lpaa6:~# grep . /proc/sys/net/ipv4/ipfrag_* ; grep FRAG /proc/net/sockstat
> /proc/sys/net/ipv4/ipfrag_high_thresh:104857600
> /proc/sys/net/ipv4/ipfrag_low_thresh:78643200
> /proc/sys/net/ipv4/ipfrag_max_dist:0
> /proc/sys/net/ipv4/ipfrag_secret_interval:0
> /proc/sys/net/ipv4/ipfrag_time:30
> FRAG: inuse 1379 memory 105006776
> 
> lpaa5:/export/hda3/google/edumazet# ./super_netperf 400 -H 10.246.7.134 -t UDP_STREAM -l 60
> netperf: send_omni: send_data failed: No route to host
> netperf: send_omni: send_data failed: No route to host
>    9063
> 
> 
> I would say that it looks pretty good to me.

Is that with an unmodifed kernel?

I would be happy if I could replicate such results. With the same
configuration I see:

[netdev9 ~]# grep . /proc/sys/net/ipv4/ipfrag_*; nstat>/dev/null; sleep 1; nstat|grep IpR; grep FRAG /proc/net/sockstat
/proc/sys/net/ipv4/ipfrag_high_thresh:104857600
/proc/sys/net/ipv4/ipfrag_low_thresh:3145728
/proc/sys/net/ipv4/ipfrag_max_dist:64
/proc/sys/net/ipv4/ipfrag_secret_interval:0
/proc/sys/net/ipv4/ipfrag_time:30
IpReasmReqds                    827385             0.0
IpReasmFails                    827385             0.0
FRAG: inuse 1038 memory 105326208

[netdev8 ~]# ./super_netperf.sh 400 -H 192.168.101.2 -t UDP_STREAM -l 60 
213.6

Note: this setup is intentionally lossy (on the sender side), to stress
the frag cache:

[netdev8 ~]#  tc -s qdisc show dev em1
qdisc mq 8001: root 
 Sent 73950097203 bytes 49639120 pkt (dropped 2052241, overlimits 0 requeues 41) 
 backlog 0b 0p requeues 41 
# ...

drops here are due to ldelay being higher than fq_codel's target (I use
fq_codel default values). Can you please share your sender's TC conf
and number of tx queues? 

Thanks,

Paolo