Sun Microsystems Systems Architecture Committee
      Subject       New Size Suffixes for mount_tmpfs
   Submitted by     Ozgur Leonard
       File         PSARC/2001/329/opinion.html
       Date         May 9th, 2001
                    Joseph Kowalski (opinion written by Lee Duncan), Lisa
     Committee      Camesano, Ralph Campbell, John Danielson, Terrence
                    Miller, Andy Rudoff, Glenn Skinner, Andrew Tucker
 Steering Committee SOESC

1. Summary

This case enhances the mount_tmpfs(1m) command so that sizes can be
specified to it in kilobytes, megabytes, gigabytes, and terabytes using
standard abbreviations. Previously, only kilobytes and megabytes could be
specified.

2. Decision & Precedence Information

The project is approved as specified in reference [1]. The project may be
delivered in an update/patch release of Solaris

3. Interfaces

                            Interfaces Exported
      Interface Name       Classification             Comment
 New size suffixes for "-o                Defined by mount_tmpfs(1m) man
 size=XXX"                 Standard       page



4. Opinion

This case was originally proposed as a fast track with a fair amount of
email discussion, which centered on the following areas.

4.1 Use of "b" To Mean Bytes

The original proposal suggested the suffix "b" stand for bytes, but
committee members suggested this conflicted with some existing commands,
such as od(1) and mkfile(1), where a size suffix of "b" is taken to mean
512-byte blocks. In addition, a suffix is not needed as a shortcut to mean
bytes, since a number with no suffix already means bytes.

        4.2 Support of "t" To Mean Terabytes

The original proposal did not suggest a suffix for terabytes, but agreed to
add it after discussion with the committee showed general agreement that
planning for future (larger) amounts of memory usage would be wise.

        4.3 Which mount(1m) Subcommands To Update

The project team originally suggested updating the mount_xmemfs(1m) command
as well as mount_tmpfs(1m), but because of size limitations in
mount_xmemfs(1m) on the IA32 platform, this command did not need the
terabyte suffix. Since mount_xmemfs(1m) already supported all the other
suffixes in this proposal, there was no need to update it.

        4.4 Need For A Common Standard and Library

Some members of the committee felt that some sort of library routine or
routines should be created to parse size specifications, including the
suffix. In this way, the duplicate work each command currently has to do to
parse these values is consolidated. In addition, this would ensure that all
commands using this interface interpreted size suffixes in the same way,
reducing end-user confusion. The project team agreed in principle, but said
that even if such a library existed, it would require major changes in this
particular case to use such a library. The committee did not want to impede
this project for a long-standing problem, so reluctantly agreed.

5. Minority Opinion(s)

None.

6. Advisory Information

The review committee advises the steering committee that some thought
should be given to creating a standard specification for size suffixes.
This standard could be implemented as one or more common library routines,
thus eliminating duplication and end-user confusion.

Appendices

Appendix A: Technical Changes Required

None

Appendix B: Technical Changes Advised

None

Appendix C: Reference Material

Unless otherwise stated, path names are relative to the case directory
(PSARC/2001/329).

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