Bug #69309 description of innodb_flush_log_at_timeout may need more explanation

Description:
description of innodb_flush_log_at_timeout:
Write and flush the logs every N seconds. This setting has an effect only when innodb_flush_log_at_trx_commit has a value of 2.

link  http://dev.mysql.com/doc/refman/5.6/en/innodb-parameters.html#sysvar_innodb_flush_log_at_t...

Actually , the master thread will  always try to write/flush logs every innodb_flush_log_at_timeout seconds, no matter how you set innodb_flush_log_at_trx_commit .

You can trace the backtrace below to confirm it :

srv_master_thread->srv_master_do_active_tasks ->srv_sync_log_buffer_in_background->log_buffer_sync_in_background

I am afraid people may be misguided by the description of innodb_flush_log_at_timeout. 

How to repeat:
read the doc

Suggested fix:
more explanation

any comment ??

Thank you for the bug report.

The description for INNODB_FLUSH_LOG_AT_TIMEOUT has been updated in the 5.6 and 5.7 reference manual. The updated description will appear in the next documentation build. 

"Write and flush the logs every "N" seconds. "innodb_flush_log_at_timeout"
was introduced in MySQL 5.6.6. It allows the timeout period between
flushes to be increased in order to reduce flushing and avoid impacting
performance of binary log group commit. Prior to MySQL 5.6.6, flushing
frequency was once per second. The default setting for
"innodb_flush_log_at_timeout" is also once per second."

Thank you for the bug report.