Bug 814822

Summary:	intermittent hangs using NFS over RDMA and large amounts of traffic
Product:	Red Hat Enterprise Linux 6	Reporter:	Mark Nipper <nipsy>
Component:	kernel	Assignee:	Honggang LI <honli>
kernel sub component:	Infiniband	QA Contact:	Filesystem QE <fs-qe>
Status:	CLOSED CURRENTRELEASE	Docs Contact:
Severity:	high
Priority:	unspecified	CC:	dledford, jshortt, nfs-maint, rwheeler, sprabhu, swhiteho
Version:	6.2
Target Milestone:	rc
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-08-15 03:49:57 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Bug Depends On:
Bug Blocks:	1269638

Description Mark Nipper 2012-04-20 19:01:01 UTC

Description of problem:
We're mounting an NFS export from a client using RDMA as the protocol over a direct HCA to HCA cable between two Mellanox MT26428 (QDR/40Gbps) Infiniband cards. Doing something simple like:
---
dd if=/dev/zero of=test bs=1024k count=10240

from the client results in this message on the server:
---
svcrdma: Error fast registering memory for xprt ffff8801a2a51c00

and these messages on the client (over several different runs of dd):
---
rpcrdma: connection to 192.168.1.1:2050 on mlx4_0, memreg 5 slots 32 ird 16
rpcrdma: connection to 192.168.1.1:2050 on mlx4_0, memreg 5 slots 32 ird 16
rpcrdma: connection to 192.168.1.1:2050 closed (-103)
rpcrdma: connection to 192.168.1.1:2050 on mlx4_0, memreg 5 slots 32 ird 16
rpcrdma: connection to 192.168.1.1:2050 closed (-103)

I don't see a kernel oops as mentioned at:
---
https://access.redhat.com/knowledge/solutions/55816#comment-360433

but the operation does take a much longer time to complete than it should and hangs intermittently throughout the writing of the file, seemingly doing nothing. So something is unhappy and disconnecting here.

Version-Release number of selected component (if applicable):
2.6.32-220.13.1.el6.x86_64 on both client and server. Let me know if you need package versions for all the related Mellanox, Infiniband, and RDMA packages. But it's all the latest of those packages in RHEL 6.2.

How reproducible:
Every time the dd command is run with a large enough file size (10GB seems sufficient to make it happen every time).

Steps to Reproduce:
1. listed above

Actual results:
File is written with huge timeouts and aggregate bandwidth is horribly slow.

Expected results:
File is written with no timeouts and bandwidth is at least approaching local disk speed.

Comment 2 RHEL Program Management 2012-05-06 04:06:47 UTC

Since RHEL 6.3 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.

Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.

Comment 16 Honggang LI 2016-08-15 03:49:57 UTC

(In reply to Mark Nipper from comment #0)
>   
> Actual results:
> File is written with huge timeouts and aggregate bandwidth is horribly slow.
> 
> Expected results:
> File is written with no timeouts and bandwidth is at least approaching local
> disk speed.

NFSoRDMA had been updated to upstream v4.1 for RHEL-6.8. The performance issue is gone.

[root@rdma-dev-00 nfsordma]$ grep -i distro /etc/motd
                           DISTRO=RHEL-6.8
[root@rdma-dev-00 nfsordma]$ rpm -q kernel
kernel-2.6.32-642.el6.x86_64
[root@rdma-dev-00 nfsordma]$ mount| grep rdma
ib0-dev-01:/home on /nfsordma type nfs (rw,rdma,port=2050,addr=172.31.0.31)
[root@rdma-dev-00 nfsordma]$ ibstat
CA 'mlx4_0'
	CA type: MT4099
	Number of ports: 2
	Firmware version: 2.36.5150
	Hardware version: 0
	Node GUID: 0x0002c90300317b10
	System image GUID: 0x0002c90300317b13
	Port 1:
		State: Active
		Physical state: LinkUp
		Rate: 56
		Base lid: 8
		LMC: 1
		SM lid: 2
		Capability mask: 0x02514868
		Port GUID: 0x0002c90300317b11
		Link layer: InfiniBand
	Port 2:
		State: Active
		Physical state: LinkUp
		Rate: 40
		Base lid: 8
		LMC: 1
		SM lid: 2
		Capability mask: 0x02514868
		Port GUID: 0x0002c90300317b12
		Link layer: InfiniBand
[root@rdma-dev-00 nfsordma]$ 
[root@rdma-dev-00 nfsordma]$ time dd if=/dev/zero of=test bs=1024k count=10240
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 64.7979 s, 166 MB/s

real	1m4.813s
user	0m0.004s
sys	0m5.061s
[root@rdma-dev-00 nfsordma]$ time dd if=/dev/zero of=test bs=1024k count=40240
40240+0 records in
40240+0 records out
42194698240 bytes (42 GB) copied, 290.3 s, 145 MB/s

real	4m52.467s
user	0m0.010s
sys	0m20.068s