Solaris Tunable Parameters Reference Manual - SCN Research

Default
Range
Units
Dynamic?
max_nprocs - reserved_procs
1 to max_nprocs - reserved_procs
Processes
No
Validation Yes. This value is compared to max_nprocs -
reserved_procs and set to the smaller of the two values.
When to Change
When you want to specify a hard limit for the number of
processes a user can create that is less than the default value of
however many processes the system can create. Attempting to
exceed this limit generates the following warning messages on
the console or in the messages file:
out of per-user processes for uid N
Commitment Level
Unstable
Paging-Related Parameters
The Solaris OS uses a demand paged virtual memory system. As the system runs,
pages are brought into memory as needed. When memory becomes occupied above a
certain threshold and demand for memory continues, paging begins. Paging goes
through several levels that are controlled by certain parameters.
The general paging algorithm is as follows:
■
■
A memory deficit is noticed. The page scanner thread runs and begins to walk
through memory. A two-step algorithm is employed:
1. A page is marked as unused.
2. If still unused after a time interval, the page is viewed as a subject for reclaim.
If the page has been modified, a request is made to the pageout thread to schedule
the page for I/O. Also, the page scanner continues looking at memory. Pageout
causes the page to be written to the page’s backing store and placed on the free list.
When the page scanner scans memory, no distinction is made as to the origin of the
page. The page might have come from a data file, or it might represent a page from
an executable’s text, data, or stack.
As memory pressure on the system increases, the algorithm becomes more
aggressive in the pages it will consider as candidates for reclamation and in how
frequently the paging algorithm runs. (For more information, see “fastscan”
on page 55 and “slowscan” on page 55.) As available memory falls between the
Chapter 2 • Solaris Kernel Tunable Parameters 47