SUMMARY: Information about kernel parameters

From: jgrijalba <jgrijalba_at_novasoft.es>
Date: Fri, 29 Jun 2001 12:04:11 +0200

Hi all,

        I've received very many responses. Thanks to: Samier Kesou, Paul Roetman,
Manish Vashi and Nick Hill.

        The original question was:

                What does per_proc_data_size, per_proc_stack_size,
max_per_proc_data_size,max_per_proc_stack_size, per_proc_address_space and
max_per_proc_address_space mean ?
                In manuals it's said, for example about per_proc_data_size and
max_per_proc_data_size:

                "The proc subsystem attributes per_proc_data_size and
max_per_proc_data_size specify the default and maximum sizes of a user
process data segment."

                a) Does This mean that when a process starts, O.S. assigns it
per_proc_data_size for its data segment and that this segment can growth
until max_per_proc_data_size ?
                b) Then, when I see examples in which per_proc_data_size is for example
4GB, I ask myself: How is possible that O.S. assigns to EVERY process 4GB
?



        Answers:


                a) Yes and no.

                        Samier Kesou:
                        ...
                        "per-proc-data-size is the current max value and will be actually used
                        for processes.
                        max-per-proc-data-size is the maximum value you can set
per-proc-data-size"
                        ...

                        Nick Hill:

                        With for example:
                        per_proc_data_segment = 134MB
                        max_per_proc_data_segment = 1GB

                        "With your proc settings the maximum space allowed for normal read/write
                        variables is by default 134MB but can be grown to 1GB. In the same way
that
                        a user can adjust these values with the ulimit command (for ksh shell,
limit
                        for csh etc) the application can do this as well ... "


                Therefore (with per_proc_data_segment = 134 MB and
max_per_proc_data_segment = 1GB for example ) when a process starts only
can reach 134MB for his data segment. If it wants to growth more than
134MB has to change per_proc_data_segment parameter for its session with
ulimit or limit but never can reach more than 1GB.



                b) As Nick Hill shows me: These parameters specify VIRTUAL segments
memory, not PHISYCAL memory.



Regards,

        Jorge Grijalba
Received on Fri Jun 29 2001 - 09:59:32 NZST

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