Will Berkeley has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/10266


Change subject: Add warnings and docs on setting block_cache_capacity_mb too 
high
......................................................................

Add warnings and docs on setting block_cache_capacity_mb too high

Raising --block_cache_capacity_mb can improve Kudu's performance, but
raising it too high (above the memory pressure threshold, which is
--memory_pressure_percentage of the hard memory limit) causes
;wq
constant flushing even if write throughput is low. This patch adds
some log messages warning about the potential problems with
setting block_cache_capacity_mb too high, as well as docs.

I chose 50% as the max recommended block cache size as a
percentage of the memory pressure threshold somewhat arbitrarily.
It seems safe, but also leaves room for allocating a large
block cache.

There's no automated tests but I did verify the expected messages
appeared in the logs when --block_cache_capacity_mb is too
high.

Change-Id: Ia99fa95c578235beb3a1c72a33a22b4d8ff4800c
---
M docs/troubleshooting.adoc
M src/kudu/cfile/block_cache.cc
M src/kudu/util/process_memory.cc
M src/kudu/util/process_memory.h
4 files changed, 40 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/66/10266/1
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Ia99fa95c578235beb3a1c72a33a22b4d8ff4800c
Gerrit-Change-Number: 10266
Gerrit-PatchSet: 1
Gerrit-Owner: Will Berkeley <[email protected]>

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