1376563 – unable to get dmstats file map to report any I/O operation stats

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Bug 1376563 - unable to get dmstats file map to report any I/O operation stats

Summary: unable to get dmstats file map to report any I/O operation stats

Keywords:
Status:	CLOSED DUPLICATE of bug 1378956
Alias:	None
Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	lvm2
Sub Component:
Version:	7.3
Hardware:	x86_64
OS:	Unspecified
Priority:	unspecified
Severity:	high
Target Milestone:	rc
Target Release:	---
Assignee:	Bryn M. Reeves
QA Contact:	cluster-qe@redhat.com
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2016-09-15 18:04 UTC by Corey Marthaler
Modified:	2021-09-03 12:37 UTC (History)
CC List:	7 users (show)
Fixed In Version:
Doc Type:	If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed:	2016-09-23 15:53:39 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Description Corey Marthaler 2016-09-15 18:04:56 UTC

Description of problem:

# Using exact same setup from bug 1376562

Verify/read all files previously written:
[root@host-117 ~]# /usr/tests/sts-rhel7.3/bin/checkit -w /mnt/lvol0 -f /tmp/checkio -v
checkit starting with:
VERIFY
Verify XIOR Stream: /tmp/checkio
Working dir:        /mnt/lvol0
[root@host-117 ~]# /usr/tests/sts-rhel7.3/bin/checkit -w /mnt/lvol0 -f /tmp/checkio -v
checkit starting with:
VERIFY
Verify XIOR Stream: /tmp/checkio
Working dir:        /mnt/lvol0
[root@host-117 ~]# /usr/tests/sts-rhel7.3/bin/checkit -w /mnt/lvol0 -f /tmp/checkio -v
checkit starting with:
VERIFY
Verify XIOR Stream: /tmp/checkio
Working dir:        /mnt/lvol0
[root@host-117 ~]# /usr/tests/sts-rhel7.3/bin/checkit -w /mnt/lvol0 -f /tmp/checkio -v
checkit starting with:
VERIFY
Verify XIOR Stream: /tmp/checkio
Working dir:        /mnt/lvol0

# No change in stat performance
[root@host-117 ~]# dmstats report --group
Name                 GrpID RgID ObjType ArID ArStart ArSize  RMrg/s WMrg/s R/s  W/s  RSz/s WSz/s AvgRqSz QSize Util% AWait RdAWait WrAWait
xjjcmoeftdcathggnism     0    0 group      0   8.63m 250.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00
vntwhckfhujdlh           1    1 group      0   9.36m 175.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00


# over write the file completely
[root@host-117 ~]# cp /root/anaconda-ks.cfg /mnt/lvol0/xjjcmoeftdcathggnism
cp: overwrite â/mnt/lvol0/xjjcmoeftdcathggnismâ? y

[root@host-117 ~]# sync
[root@host-117 ~]# echo 3 > /proc/sys/vm/drop_caches

# No change
[root@host-117 ~]# dmstats report --group
Name                 GrpID RgID ObjType ArID ArStart ArSize  RMrg/s WMrg/s R/s  W/s  RSz/s WSz/s AvgRqSz QSize Util% AWait RdAWait WrAWait
xjjcmoeftdcathggnism     0    0 group      0   8.63m 250.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00
vntwhckfhujdlh           1    1 group      0   9.36m 175.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00



 
# write and read zeros over and over
[root@host-117 ~]# for i in $(seq 0 20)
> do
> dd if=/dev/zero of=/mnt/lvol0/xjjcmoeftdcathggnism oflag=direct,sync bs=1M count=15
> dd if=/mnt/lvol0/xjjcmoeftdcathggnism of=/dev/null iflag=direct,sync bs=1M count=15
> done

# No change
[root@host-117 ~]# dmstats report --group
Name                 GrpID RgID ObjType ArID ArStart ArSize  RMrg/s WMrg/s R/s  W/s  RSz/s WSz/s AvgRqSz QSize Util% AWait RdAWait WrAWait
xjjcmoeftdcathggnism     0    0 group      0   8.63m 250.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00
vntwhckfhujdlh           1    1 group      0   9.36m 175.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00

[root@host-117 ~]# echo 3 > /proc/sys/vm/drop_caches
[root@host-117 ~]# sync

# Still no change
[root@host-117 ~]# dmstats report --group
Name                 GrpID RgID ObjType ArID ArStart ArSize  RMrg/s WMrg/s R/s  W/s  RSz/s WSz/s AvgRqSz QSize Util% AWait RdAWait WrAWait
xjjcmoeftdcathggnism     0    0 group      0   8.63m 250.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00
vntwhckfhujdlh           1    1 group      0   9.36m 175.00k   0.00   0.00 0.00 0.00     0     0       0  0.00  0.00  0.00    0.00    0.00


Version-Release number of selected component (if applicable):
3.10.0-501.el7.x86_64

lvm2-2.02.165-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
lvm2-libs-2.02.165-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
lvm2-cluster-2.02.165-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
device-mapper-1.02.134-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
device-mapper-libs-1.02.134-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
device-mapper-event-1.02.134-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
device-mapper-event-libs-1.02.134-2.el7    BUILT: Wed Sep 14 09:01:43 CDT 2016
device-mapper-persistent-data-0.6.3-1.el7    BUILT: Fri Jul 22 05:29:13 CDT 2016

Comment 2 Bryn M. Reeves 2016-09-16 09:25:37 UTC

I think the reason you're not actually re-writing the file - by default I think cp will unlink the destination and open(2) a new file, where dd does open the existing file, but using O_CREAT|O_TRUNC (i.e. all existing extents are released):

lseek(0, 0, SEEK_CUR)                   = 0
open("/var/tmp/foo", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
dup2(3, 1)                              = 1

This will be fixed when we implement inode monitoring and automatic refresh of the region table but until then we can only support in-place IO.

Comment 3 Bryn M. Reeves 2016-09-16 09:26:59 UTC

We should note this in the man page/release notes, or a kbase article - it's going to be fairly common with tools like cp/dd and is confusing for the user.

Comment 6 Bryn M. Reeves 2016-09-23 15:53:39 UTC


*** This bug has been marked as a duplicate of bug 1378956 ***

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