MySQL Bugs: #34563: open_files_limit calculation wrong in manual

Bug #34563	open_files_limit calculation wrong in manual
Submitted:	14 Feb 2008 19:11	Modified:	16 Jun 2008 15:49
Reporter:	Kyle Joiner	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	5.0	OS:	Any
Assigned to:	Paul DuBois	CPU Architecture:	Any

Description:
The Manual states:
Change the number of file descriptors available to mysqld. If this option is not set or is set to 0, mysqld uses the value to reserve file descriptors with setrlimit(). If the value is 0, mysqld reserves max_connections×5 or max_connections + table_open_cache×2 files (whichever is larger). You should try increasing this value if mysqld gives you the error Too many open files.

Where the code says:
2742
2743 /* MyISAM requires two file handles per table. */
2744 wanted_files= 10+max_connections+table_cache_size*2;
2745 /*
2746 We are trying to allocate no less than max_connections*5 file
2747 handles (i.e. we are trying to set the limit so that they will
2748 be available). In addition, we allocate no less than how much
2749 was already allocated. However below we report a warning and
2750 recompute values only if we got less file handles than were
2751 explicitly requested. No warning and re-computation occur if we
2752 can't get max_connections*5 but still got no less than was
2753 requested (value of wanted_files).
2754 */
2755 max_open_files= max(max(wanted_files, max_connections*5),
2756 open_files_limit);
2757 files= my_set_max_open_files(max_open_files);
2758

The code indicates a different calculation than the manual shows and that the comparison does not look at it being set to 0 to perform calculation.

How to repeat:
look at code versus manual.

Suggested fix:
verify which is correct and correct manual if necessary.

The code is correct, docs should be updated.
Or rather, I wonder why we need to document the exact formula?
It may change as the server gets new modules and starts using more open files.

Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly, and will be included in the next release of the relevant products.