Re: teraspace, user spaces, etc.

["Steve Richter" <srichter@xxxxxxxxxxxxx>]

Paul, anyone else on the list,

Could you review the following and correct it, add to it?

Single level storage ( sls ):

The 64 bit addr space is divided into 16M segments.

Each segment is composed of 512 byte pages.

Each page of the segment that is USED is assigned an aux storage addr.

The aux storage addr of a page is NOT contiguous with adjacent pages in the
segment??

When the segment page is referenced by a running pgm it is paged into main
storage and given a main storage addr by the virtual memory mgr.

The main storage addr of a page is NOT contiguous with adjacent pages in the
segment.

A single table could be used to locate the aux storage and main storage addr
of a segment page. Call it the sls page addr table ( slspat ). This table
would have the following layout:
    segment nbr
    page nbr
    aux storage addr
    main storage addr

The addr component of a 16 byte ptr consists of segment nbr and offset from
the start of the segment.

The offset is divided by the page size giving a page nbr and offset within
the page.

The ptr addr segment page nbr is located in the slspat.

The main storage addr of the segment page is used by the cpu to reference
the data addressed by the ptr.


Is that right, too simplistic, have I veered off the road??

I am esp interested in knowing that if the segment pages are not contiguous,
how are they virtualized to appear contiguous. When I CpyNv to a bin(4) var
located at ofs 510 of the segment, what happens that enables the 1st two
bytes to be placed at the end of page1 of the segment and the 2nd two bytes
at the start of page2?

Thanks much,

Steve Richter


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