Joe McDonnell has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/20919


Change subject: IMPALA-12669: Ignore loop devices for DiskIoMgr
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IMPALA-12669: Ignore loop devices for DiskIoMgr

Loop devices are read-only devices mounting a file's contents.
Ubuntu uses loop devices extensively for snap packages
(e.g. on one development system, there are 18 loop devices).
Right now, Impala is allocating DiskIoMgr threads for these
loop devices. Since it believes they are not rotational devices,
each loop device gets 8 threads, and this is doubled due to
HDFS monitoring threads. These extra threads slow down
processing minidumps and debugging with gdb.

>From Impala's point of view, loop devices are unlikely to be
interesting. This detects loop devices and avoids allocating
DiskIoMgr threads for them.

Testing:
 - Hand tested on my development machine, which has many snap
   packages.

Change-Id: Ic09230e465f78d55876909453e8a7e39d9a89c4c
---
M be/src/util/disk-info.cc
1 file changed, 12 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/19/20919/1
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Ic09230e465f78d55876909453e8a7e39d9a89c4c
Gerrit-Change-Number: 20919
Gerrit-PatchSet: 1
Gerrit-Owner: Joe McDonnell <[email protected]>

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