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Bug 2127397 - nfsrahead - the config file cannot set the read_ahead_kb value as expected
Summary: nfsrahead - the config file cannot set the read_ahead_kb value as expected
Keywords:
Status: CLOSED MIGRATED
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: nfs-utils
Version: 8.7
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Steve Dickson
QA Contact: Yongcheng Yang
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-09-16 07:54 UTC by Yongcheng Yang
Modified: 2023-09-23 11:15 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2023-09-23 11:15:54 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker   RHEL-7892 0 None Migrated None 2023-09-23 11:15:49 UTC
Red Hat Issue Tracker RHELPLAN-134149 0 None None None 2022-09-16 08:06:06 UTC

Description Yongcheng Yang 2022-09-16 07:54:52 UTC 
Description of problem:
After the `nfsrahead` introduced via Bug 1946283 the automatic testcase gets to be failed sometimes as the result read_ahead_kb value doesn't match what the config file set.

But it's weird that when I check that by hand it turns to work as expected. Finally I find this problem can be reliablely reproduced in arch s390x. Please help check it.

Version-Release number of selected component (if applicable):
nfs-utils-2.3.3-57.el8

How reproducible:
always in arch s390x

Steps to Reproduce:
1. Configure nfsrahead in /etc/nfs.conf
2. Mount and check read_ahead_kb value
3.


Actual results:
[root@ibm-z-509 ~]# cat /etc/exports
/export_test *(rw,no_root_squash)
[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 nfs=15000
 nfs4=16000           <<<<<<<<<<<<<<
 default=128
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=3
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
334 95 0:45 / /mnt_test rw,relatime shared:178 - nfs localhost:/export_test/ rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:45/read_ahead_kb
15000
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                   <<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]# rpm -q kernel nfs-utils
kernel-4.18.0-425.el8.s390x
nfs-utils-2.3.3-57.el8.s390x
[root@ibm-z-509 ~]#

Expected results:


Additional info:
Comment 1 Yongcheng Yang 2022-09-16 08:09:09 UTC 
Looks like the "nfs4" and "default" settings are messing up.

[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 nfs=15000
 default=256                    <<<<<<<<<<<<<< IMO the v4 mount use this default value
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=2$5,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                             <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]#



[root@ibm-z-509 ~]# vi /etc/nfs.conf
[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 nfs=256
 nfs4=16000                    <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=2$5,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                             <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=3
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
334 95 0:45 / /mnt_test rw,relatime shared:178 - nfs localhost:/export_test/ rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,
hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:45/read_ahead_kb
256
[root@ibm-z-509 ~]# umount /mnt_test/


[root@ibm-z-509 ~]# vi /etc/nfs.conf
[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 default=256                    <<<<<<<<<<<<<< IMO both v3 and v4 mount use this default value
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=3
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
334 95 0:45 / /mnt_test rw,relatime shared:178 - nfs localhost:/export_test/ rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:45/read_ahead_kb
256
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                             <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]#
Comment 2 Yongcheng Yang 2022-10-20 02:19:14 UTC 
Looks like there're more than one issue for now:

1. Within KVM hypervisor it fails to config the nfsrahead value randomly, e.g.
 - fail in KVM https://beaker.engineering.redhat.com/jobs/7137086
 - pass in non-KVM https://beaker.engineering.redhat.com/jobs/7137194


2. In arch s390x, the v4 config doesn't work and seemingly it always use the default value "128":
 - https://beaker.engineering.redhat.com/recipes/12794496
 ...
[09:52:08 root@ ~~]# mount -t nfs localhost:/exportdir /mnt/nfsmp -o vers=4.2
[09:52:08 root@ ~~]# cat /proc/self/mountinfo | grep /mnt/nfsmp
334 95 0:47 / /mnt/nfsmp rw,relatime shared:176 - nfs4 localhost:/exportdir rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[09:52:08 root@ ~~]# /usr/libexec/nfsrahead -F -d 0:47
nfsrahead: setting /mnt/nfsmp readahead to 16000

16000
[09:52:08 root@ ~~]# cat /sys/class/bdi/0:47/read_ahead_kb
128


3. In arch ppc64le, sometimes the effect value is a bit lower than what we set:
 - https://beaker.engineering.redhat.com/recipes/12794501
 ...
[11:47:36 root@ ~~]# mount -t nfs localhost:/exportdir /mnt/nfsmp -o vers=3
[11:47:36 root@ ~~]# cat /proc/self/mountinfo | grep /mnt/nfsmp
413 96 0:46 / /mnt/nfsmp rw,relatime shared:217 - nfs localhost:/exportdir rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[11:47:36 root@ ~~]# /usr/libexec/nfsrahead -F -d 0:46
nfsrahead: setting /mnt/nfsmp readahead to 15000

15000
[11:47:37 root@ ~~]# cat /sys/class/bdi/0:46/read_ahead_kb
14976
Comment 4 RHEL Program Management 2023-09-23 11:15:26 UTC 
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.
Comment 5 RHEL Program Management 2023-09-23 11:15:54 UTC 
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