netdev - Re: Slow veth performance over ipoib interface on 4.7.0 (and earlier) (Was Re: [IPOIB] Excessive TX packet drops due to IPOIB_MAX_PATH_REC

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Date:	Thu, 04 Aug 2016 10:08:28 -0400
From:	Doug Ledford <dledford@...hat.com>
To:	Nikolay Borisov <kernel@...p.com>,
	Erez Shitrit <erezsh@....mellanox.co.il>
Cc:	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: Slow veth performance over ipoib interface on 4.7.0 (and
 earlier) (Was Re: [IPOIB] Excessive TX packet drops due to
 IPOIB_MAX_PATH_REC_QUEUE)

On Thu, 2016-08-04 at 16:34 +0300, Nikolay Borisov wrote:
> 
> On 08/01/2016 11:56 AM, Erez Shitrit wrote:
> > 
> > The GID (9000:0:2800:0:bc00:7500:6e:d8a4) is not regular, not from
> > local subnet prefix.
> > why is that?
> > 
> 
> So I managed to debug this and it tuns out the problem lies between
> veth
> and ipoib interaction:
> 
> I've discovered the following strange thing. If I have a vethpair
> where
> the 2 devices are in a different net namespaces as shown in the
> scripts
> I have attached then the performance of sending a file, originating
> from
> the veth interface inside the non-init netnamespace, going across the
> ipoib interface is very slow (100kb). For simple reproduction I'm
> attaching
> 2 scripts which have to be run on 2 machine and the respective ip
> addresses
> set on them. Then sending node woult initiate a simple file copy over
> NC.
> I've observed this behavior on upstream 4.4, 4.5.4 and 4.7.0 kernels
> both
> with ipv4 and ipv6 addresses. Here is what the debug log of the ipoib
> module shows:
> 
> ib%d: max_srq_sge=128
> ib%d: max_cm_mtu = 0xfff0, num_frags=16
> ib0: enabling connected mode will cause multicast packet drops
> ib0: mtu > 4092 will cause multicast packet drops.
> ib0: bringing up interface
> ib0: starting multicast thread
> ib0: joining MGID ff12:401b:ffff:0000:0000:0000:ffff:ffff
> ib0: restarting multicast task
> ib0: adding multicast entry for mgid
> ff12:601b:ffff:0000:0000:0000:0000:0001
> ib0: restarting multicast task
> ib0: adding multicast entry for mgid
> ff12:401b:ffff:0000:0000:0000:0000:0001
> ib0: join completion for ff12:401b:ffff:0000:0000:0000:ffff:ffff
> (status 0)
> ib0: Created ah ffff88081063ea80
> ib0: MGID ff12:401b:ffff:0000:0000:0000:ffff:ffff AV
> ffff88081063ea80, LID 0xc000, SL 0
> ib0: joining MGID ff12:601b:ffff:0000:0000:0000:0000:0001
> ib0: joining MGID ff12:401b:ffff:0000:0000:0000:0000:0001
> ib0: successfully started all multicast joins
> ib0: join completion for ff12:601b:ffff:0000:0000:0000:0000:0001
> (status 0)
> ib0: Created ah ffff880839084680
> ib0: MGID ff12:601b:ffff:0000:0000:0000:0000:0001 AV
> ffff880839084680, LID 0xc002, SL 0
> ib0: join completion for ff12:401b:ffff:0000:0000:0000:0000:0001
> (status 0)
> ib0: Created ah ffff88081063e280
> ib0: MGID ff12:401b:ffff:0000:0000:0000:0000:0001 AV
> ffff88081063e280, LID 0xc004, SL 0
> 
> When the transfer is initiated I can see the following errors
> on the sending node:
> 
> ib0: PathRec status -22 for GID
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: neigh free for 000003 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: Start path record lookup for
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: PathRec status -22 for GID
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: neigh free for 000003 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: Start path record lookup for
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: PathRec status -22 for GID
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: neigh free for 000003 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: Start path record lookup for
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: PathRec status -22 for GID
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: Start path record lookup for
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: PathRec status -22 for GID
> 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: neigh free for 000003 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> ib0: neigh free for 000003 0401:0000:1400:0000:a0a8:ffff:1c01:4d36
> 
> Here is the port guid of the sending node: 0x0011750000772664 and
> on the receiving one: 0x0011750000774d36
> 
> Here is how the paths look like on the sending node, 
> clearly the paths being requested from the veth interface
> 
> cat /sys/kernel/debug/ipoib/ib0_path
> GID: 401:0:1400:0:a0a8:ffff:1c01:4d36
> complete: no
> 
> GID: 401:0:1400:0:a410:ffff:1c01:4d36
> complete: no
> 
> GID: fe80:0:0:0:11:7500:77:2a1a
> complete: yes
> DLID: 0x0004
> SL: 0
> rate: 40.0 Gb/sec
> 
> GID: fe80:0:0:0:11:7500:77:4d36
> complete: yes
> DLID: 0x000a
> SL: 0
> rate: 40.0 Gb/sec
> 
> Testing the same scenario but instead of using veth devices I create
> the device in the non-init netnamespace via the following commands
> I can achieve sensible speeds:
> ip link add link ib0 name ip1 type ipoib
> ip link set dev ip1 netns test-netnamespace
> 
> 
> 
> 
>  
> [Snipped a lot of useless stuff]

The poor performance sounds a duplicate of the issue reported by Roland
and in the upstream kernel bugzilla 111921.  That would be the IPoIB
routed packet performance issue.

-- 
Doug Ledford <dledford@...hat.com>
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