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sysmap: rmap overflow

This is the result of the resource map filling up. The resource map contains entries for each area of free virtual memory. If virtual memory is fragmented into mant small chunks, there can be so many entries in rmap that an overflow occurs.

The resource map can be increased by increasing the nproc kernel parameter. The actual increase required is a matter of trial and error. Decreasing the ninode parameter can also decrease the amount of virtual memory fragmentation that occurs.

Buffer Cache

This is the area of memory used by programs when writing to disk. Programs write to buffer cache instead of disk to speed things up. The cache is then written in large chunks. nbuf and bufpages control the size of this area of memory. If values are set for these parameters, fixed sizes are set. However, if the value is set to zero, dynamic buffer cache is enabled. The OS then decides how much it needs. The ammount of dynamic buffer cache available is controlled by dbc_min_pct and dbc_max_pct. These control the minimum and maximum amount of buffer cache that can be allocated as a percentage of the total memory available. For HP-UX 10.20, HP recommend the use of dynamic buffer cache.

Programs and Kernel Parameters

A program in memory consists of:

• 1 code (text) segment. The maximum size of this is controlled by maxtsiz. This needs to be a big as your binary.
• 1 data (heap) segment. The maximim size of this is controlled by maxdsiz. Default is 67Mb. Max. for 10.x is 900Mb.
• 1 stack segment. The maximum size of this is controlled by maxssiz. The default is 8Mb which is usually enough. The max. is 80Mb.