[kafka] branch trunk updated: KAFKA-6343 Documentation update in OS-level tuning section: add vm.ma… (#4358)

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The following commit(s) were added to refs/heads/trunk by this push:
     new bf0675a  KAFKA-6343 Documentation update in OS-level tuning section: add vm.ma… (#4358)
bf0675a is described below

commit bf0675ac5f31d67a1c75baf211475b8fc98f1ef1
Author: Alex Dunayevsky <ro...@users.noreply.github.com>
AuthorDate: Wed Aug 22 20:13:10 2018 +0300

    KAFKA-6343 Documentation update in OS-level tuning section: add vm.ma… (#4358)
    
    Reviewers: Manikumar Reddy O <ma...@gmail.com>, Ismael Juma <is...@juma.me.uk>, Jun Rao <ju...@gmail.com>
---
 docs/ops.html | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/docs/ops.html b/docs/ops.html
index 9d4f6cc..d57f1cf 100644
--- a/docs/ops.html
+++ b/docs/ops.html
@@ -705,10 +705,11 @@
   <p>
   We have seen a few issues running on Windows and Windows is not currently a well supported platform though we would be happy to change that.
   <p>
-  It is unlikely to require much OS-level tuning, but there are two potentially important OS-level configurations:
+  It is unlikely to require much OS-level tuning, but there are three potentially important OS-level configurations:
   <ul>
-      <li>File descriptor limits: Kafka uses file descriptors for log segments and open connections.  If a broker hosts many partitions, consider that the broker needs at least (number_of_partitions)*(partition_size/segment_size) to track all log segments in addition to the number of connections the broker makes.  We recommend at least 100000 allowed file descriptors for the broker processes as a starting point.
+      <li>File descriptor limits: Kafka uses file descriptors for log segments and open connections.  If a broker hosts many partitions, consider that the broker needs at least (number_of_partitions)*(partition_size/segment_size) to track all log segments in addition to the number of connections the broker makes. We recommend at least 100000 allowed file descriptors for the broker processes as a starting point. Note: The mmap() function adds an extra reference to the file associated with [...]
       <li>Max socket buffer size: can be increased to enable high-performance data transfer between data centers as <a href="http://www.psc.edu/index.php/networking/641-tcp-tune">described here</a>.
+      <li>Maximum number of memory map areas a process may have (aka vm.max_map_count). <a href="http://kernel.org/doc/Documentation/sysctl/vm.txt">See the Linux kernel documentation</a>. You should keep an eye at this OS-level property when considering the maximum number of partitions a broker may have. By default, on a number of Linux systems, the value of vm.max_map_count is somewhere around 65535. Each log segment, allocated per partition, requires a pair of index/timeindex files, an [...]
   </ul>
   <p>