Hello Tidy Bot, Alexey Serbin, Ashwani Raina, Kudu Jenkins, Abhishek Chennaka, 
Wang Xixu,

I'd like you to reexamine a change. Please visit

    http://gerrit.cloudera.org:8080/20166

to look at the new patch set (#19).

Change subject: KUDU-3407 Avoid unchecked scheduling of flush operations.
......................................................................

KUDU-3407 Avoid unchecked scheduling of flush operations.

In some clusters, the memory usages of tservers might be 60% ~ 80%
for a long time. During this time the maintenance manager will not
run any operation other than wal gc and MRS/DRS flushes, which will
make the performance of tservers worse and worse and eventually break
due to OOM.

This patch add an argument to give a chance to do other ops while
server is under memory pressure.

This mechanism works when the memory usage between
memory_pressure_percentage and memory_limit_soft_percentage.
Higher the memory usage is, higher the probability to flush
MRS/DMS.

e.g.
memory_pressure_percentage = 60%
memory_limit_soft_percentage = 80%
The probability of not flushing MRS/DMS is the value of
run_non_memory_ops_prob, which is 0.2 by default, when the memory
usage is 60%.
As the memory increases, it gradually decreases to 0, when the
memory usage is 80%.

Change-Id: Idc2fd3a850cf99d54ef2980211b712468440ed80
---
M src/kudu/util/maintenance_manager-test.cc
M src/kudu/util/maintenance_manager.cc
M src/kudu/util/maintenance_manager.h
3 files changed, 222 insertions(+), 10 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/66/20166/19
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Idc2fd3a850cf99d54ef2980211b712468440ed80
Gerrit-Change-Number: 20166
Gerrit-PatchSet: 19
Gerrit-Owner: Song Jiacheng <songjiach...@thinkingdata.cn>
Gerrit-Reviewer: Abhishek Chennaka <achenn...@cloudera.com>
Gerrit-Reviewer: Alexey Serbin <ale...@apache.org>
Gerrit-Reviewer: Ashwani Raina <ara...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Song Jiacheng <songjiach...@thinkingdata.cn>
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Reviewer: Wang Xixu <1450306...@qq.com>

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