Hello Marton Greber, Alexey Serbin, Yingchun Lai, Kudu Jenkins, Wang Xixu, 

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

    http://gerrit.cloudera.org:8080/20716

to look at the new patch set (#10).

Change subject: [util] add a warning into 'heap_sample_every_n_bytes' flag 
description.
......................................................................

[util] add a warning into 'heap_sample_every_n_bytes' flag description.

Parameter --heap_sample_every_n_bytes is actually a parameter of
tcmalloc. Setting it to a positive value will make thread
cache request some sample allocations from page cache, which
will compete the lock of page heap with other threads. So does
the free operation of the sample.

A tserver with high throughput(especially for upserts) might lose
so much performance because of the lock contention of tcmalloc,
Almost all the apply threads are waiting for the spin lock.

So give a warning on the --heap_sample_every_n_bytes in case that
some users do not know the terrible influence of this parameter.

Change-Id: I00d55126f0cad0ac6cc130576cc45808f96f0a47
---
M src/kudu/util/flags.cc
1 file changed, 14 insertions(+), 2 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/16/20716/10
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I00d55126f0cad0ac6cc130576cc45808f96f0a47
Gerrit-Change-Number: 20716
Gerrit-PatchSet: 10
Gerrit-Owner: Song Jiacheng <songjiach...@thinkingdata.cn>
Gerrit-Reviewer: Alexey Serbin <ale...@apache.org>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Marton Greber <greber...@gmail.com>
Gerrit-Reviewer: Song Jiacheng <songjiach...@thinkingdata.cn>
Gerrit-Reviewer: Wang Xixu <1450306...@qq.com>
Gerrit-Reviewer: Yingchun Lai <laiyingc...@apache.org>

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