Song Jiacheng has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/20716


Change subject: Issue a warning on parameter heap_sample_every_n_bytes.
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Issue a warning on parameter heap_sample_every_n_bytes.

Parameter heap_sample_every_n_bytes is actually a parameter of
tcmalloc. Setting it to a value greater than 0 will make thread
cache request to page heap for some sample allocations, which
will occupy the lock of page heap. So does the free opeation
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, even if
setting the parameter to a higher value like 1M.

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

Change-Id: I00d55126f0cad0ac6cc130576cc45808f96f0a47
---
M src/kudu/util/flags.cc
1 file changed, 4 insertions(+), 2 deletions(-)



  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/16/20716/1
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I00d55126f0cad0ac6cc130576cc45808f96f0a47
Gerrit-Change-Number: 20716
Gerrit-PatchSet: 1
Gerrit-Owner: Song Jiacheng <[email protected]>

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