Change in vdsm[master]: misc: Support zero-time in getReadDelay()

danken at redhat.com danken at redhat.com
Thu Mar 26 00:21:48 UTC 2015


Dan Kenigsberg has submitted this change and it was merged.

Change subject: misc: Support zero-time in getReadDelay()
......................................................................


misc: Support zero-time in getReadDelay()

We found out that dd returned the following output:

    "517 bytes (517 B) copied, 0 s, Infinity B/s"

The root cause for getting zero/Infinity stats in dd is erratic
behavior of clock_gettime. Testing in the field shows that
clock_gettime() using CLOCK_MONOTONIC may return the same value
for duration of up to 11 milliseconds.

We ran a tool sampling current time using clock_gettime(), and
recording the uniqe readings and the difference between the
previous and the current sample:

    #samples  difference
     177      0.000000001
     175      0.000999812
    9462      0.000999813
     183      0.000999814
       1      0.001999626
       1      0.010997944
       1      0.011997756

In dd, if the start time is equal to the end time, dd returns
"0 s, Infinity B/s"

misc.readpeed() fails to parse that output. This causes the domain
monitor to fail and the domain to move into invalid state. This failure
could cause the host to become non-operational, leading to migration
storm while storage is actually valid.

misc.readpeed() changed to parse the returned output.

Engine tested and is not affected by this change.

Change-Id: I58ae0ec5f3f88a1738ef1b95688534c8c8022362
Bug-Url: https://bugzilla.redhat.com/1191549
Signed-off-by: Ala Hino <ahino at redhat.com>
Signed-off-by: Tobias Fiebig <tfiebig at wybt.net>
Reviewed-on: https://gerrit.ovirt.org/38082
Reviewed-by: Nir Soffer <nsoffer at redhat.com>
Reviewed-by: Adam Litke <alitke at redhat.com>
---
M tests/miscTests.py
M vdsm/storage/misc.py
2 files changed, 4 insertions(+), 2 deletions(-)

Approvals:
  Adam Litke: Looks good to me, approved
  Nir Soffer: Looks good to me, but someone else must approve
  Ala Hino: Verified



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Gerrit-MessageType: merged
Gerrit-Change-Id: I58ae0ec5f3f88a1738ef1b95688534c8c8022362
Gerrit-PatchSet: 5
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Ala Hino <ahino at redhat.com>
Gerrit-Reviewer: Adam Litke <alitke at redhat.com>
Gerrit-Reviewer: Ala Hino <ahino at redhat.com>
Gerrit-Reviewer: Allon Mureinik <amureini at redhat.com>
Gerrit-Reviewer: Dan Kenigsberg <danken at redhat.com>
Gerrit-Reviewer: Daniel Erez <derez at redhat.com>
Gerrit-Reviewer: Federico Simoncelli <fsimonce at redhat.com>
Gerrit-Reviewer: Liron Aravot <laravot at redhat.com>
Gerrit-Reviewer: Nir Soffer <nsoffer at redhat.com>
Gerrit-Reviewer: Shirly Radco <sradco at redhat.com>
Gerrit-Reviewer: automation at ovirt.org
Gerrit-Reviewer: oVirt Jenkins CI Server


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