MySQL Bugs: #32479: large_page

Bug #32479	large_page_size undocumented
Submitted:	18 Nov 2007 15:00	Modified:	23 Nov 2007 16:20
Reporter:	Mark Leith	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	all	OS:	Any
Assigned to:	Jon Stephens	CPU Architecture:	Any
Tags:	large page support

Description:
The large_page_size system variable is undocumented, although large_pages is documented:

mysql> show variables like 'large_page%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| large_page_size | 0     | 
| large_pages     | OFF   | 
+-----------------+-------+
2 rows in set (0.00 sec)

How to repeat:
Try to find 'large_page_size' in the manual. 

Suggested fix:
Add documentation for this variable. Investigation of the source shows that it is set via my_get_large_page_size() and my_get_large_page_size_int() (within mysys/my_largepage.c), by looking in /proc/meminfo and getting the information for Hugepagesize:

#ifdef HUGETLB_USE_PROC_MEMINFO
/* Linux-specific function to determine the size of large pages */

uint my_get_large_page_size_int(void)
{
  FILE *f;
  uint size = 0;
  char buf[256];
  DBUG_ENTER("my_get_large_page_size_int");

  if (!(f = my_fopen("/proc/meminfo", O_RDONLY, MYF(MY_WME))))
    goto finish;

  while (fgets(buf, sizeof(buf), f))
    if (sscanf(buf, "Hugepagesize: %u kB", &size))
      break;

  my_fclose(f, MYF(MY_WME));
  
finish:
  DBUG_RETURN(size * 1024);
}
#endif /* HUGETLB_USE_PROC_MEMINFO */

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.