[LU-715] Value read from qos_threshold_rr file does not match value written

• Status: Resolved
• Project: Lustre
• Affects Version/s: Lustre 1.8.6
• Fix Version/s: Lustre 2.2.0, Lustre 1.8.8
• Type: Bug
• Priority: Minor
• Reporter: Rick Mohr
• Assignee: Andreas Dilger
• Resolution: Fixed

Environment

CentOS 5.6

Description

After I change the value of qos_threshold_rr by writing to /proc/fs/lustre/lov/<fsname>-mdtlov/qos_threshold_rr, the value I read back is usually one less than the value I wrote:

[root]# echo 17 > qos_threshold_rr
[root]# cat qos_threshold_rr
16%

This is not the case for values 0 or 100:

[root]# echo 100 > qos_threshold_rr
[root]# cat qos_threshold_rr
100%
[root]# echo 0 > qos_threshold_rr
[root]# cat qos_threshold_rr
0%

I realize this is an artifact of the way the value is stored. (Value range 0-100 is converted to 0-256 when written, and then converted back when read.) However, it is confusing to write one value and then read back a different value. This could be especially problematic when the value is 1:

[root]# echo 1 > qos_threshold_rr
[root]# cat qos_threshold_rr
0%

Anyone reading a value of 0 would not know whether the value had been set to 0 or 1.

If the behavior of Lustre cannot be modified, then the documentation should probably be updated to explain it.

Comments

[Andreas Dilger]

Since the value in the kernel is finer grained than the value from userspace, it should be possible to always return the original value by rinsing to the nearest integer at conversion instead of truncating. It should be relatively simple to fix in Lustre.

[Matt Ezell]

Patch for b1_8 is at http://review.whamcloud.com/1522

[Matt Ezell]

Patch against master is at http://review.whamcloud.com/1532

[Peter Jones]

Andreas please select a second inspector if something other than Oleg needs to inspect this too

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,el5,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,el6,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,server,el5,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,sles11,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,server,el6,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,ubuntu1004,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,server,el5,ofa #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,el5,ofa #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Peter Jones]

Landed for 2.2

[Build Master (Inactive)]

Integrated in lustre-master » i686,server,el5,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,client,el6,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,client,el5,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,client,el5,ofa #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = FAILURE
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,server,el5,ofa #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,server,el6,inkernel #322
LU-715 lov: fix procfs reporting for qos values (Revision 0d0b8d65d84c644290f938a43fdcb0d68015c519)

Result = SUCCESS
Oleg Drokin : 0d0b8d65d84c644290f938a43fdcb0d68015c519
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » x86_64,client,el5,ofa #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » x86_64,client,el6,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » x86_64,server,el5,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » i686,client,el6,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » x86_64,client,el5,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » x86_64,client,ubuntu1004,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » i686,client,el5,ofa #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » x86_64,server,el5,ofa #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » i686,client,el5,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » i686,server,el5,inkernel #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Build Master (Inactive)]

Integrated in lustre-b1_8 » i686,server,el5,ofa #160
LU-715 lov: fix procfs reporting for qos values (Revision d07942a89ba92fa20cf0364900a1d52d94784edc)

Result = SUCCESS
Johann Lombardi : d07942a89ba92fa20cf0364900a1d52d94784edc
Files :

• lustre/lov/lproc_lov.c

[Andreas Dilger]

Patch was landed for Lustre 2.2.