MySQL Bugs: #54762: need to optimize the flush list code, buf_flush

Bug #54762	need to optimize the flush list code, buf_flush_batch() function
Submitted:	24 Jun 2010 6:42
Reporter:	Shane Bester (Platinum Quality Contributor)	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: InnoDB Plugin storage engine	Severity:	S4 (Feature request)
Version:	plugin 1.0.9, innodb 1.1.1	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
This is a request to get rid of the requirement to hold buf_pool_mutex 
during this function.

It's also needed that the O(n²) algorithm be turned into O(n).
When the scan from the end of the LRU is restarted once for each page for which buf_flush_ready_for_flush() returns true. That will revisit pages on the LRU chain many times and if the last N elements of the LRU chain are ready for flushing, then this can visit N*N elements of the list.

How to repeat:
It's a known issue.  Read code, or chat to #innodb team.

Can this be closed as fixed? 5.6 implemented hazard pointers for flush list flushes, 5.7 implemented them for LRU list flushes, and 5.6.16 has a hack to avoid LRU scan restarts.