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confused by page/pagelet size

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Regular Advisor

confused by page/pagelet size

System Management I - Page 6-39
6.11.1 indicates that "A page on a VAX system is 512 bytes. On Alpha System it's 8KB"

Performance Management I - Page 3-1
3.1 indicates that "On Alpha systems... A pagelet is equal to a VAX page, or 512KB

that's the contradiction.
the 1st says page on VAX is 512B but 2nd says it's 512KB
the 2nd says pagelet on Alpha is 8K but 2nd says it's 512KB

also, Performance Management I - Page 8-2
Term: Block is defined as 521 bytes
but i remember that 1 block = 512 KB... confused again...

which is correct? or who knows the exact value?
David B Sneddon
Honored Contributor

Re: confused by page/pagelet size


It is a typo -- a VAX page is 512 BYTES.
A pagelet is 512 BYTES.
An Alpha page is 8K BYTES.
1 block is 512 BYTES.

Regular Advisor

Re: confused by page/pagelet size

ok! thanks a lot !
Ian Miller.
Honored Contributor

Re: confused by page/pagelet size

On a Itanium VMS system the page size appears t be 8K in current systems but this may change.
Purely Personal Opinion
John Travell
Valued Contributor

Re: confused by page/pagelet size

Just for the record, there is neither a typo nor an error.
On both VAX and Alpha the PAGE is the smallest unit of memory management accessable by a process. A human problem arises when the natural size of a SYSGEN parameter is a PAGE.
How do people cope with remembering that 'this' parameter on a VAX is (say) 16384, and 1024 on an Alpha. In order to eliminate this potential for serious problems, the concept of the PAGELET was created. In the Alpha 'this' parameter is described in pagelets, and set to a comparable value as on the VAX, then internally converted to PAGES.
For an example, do
$ mc sysgen show SYSMWCNT
SYSMWCNT 4022 2048 512 1048576 Pagelets
internal value 252 128 32 65536 Pages

There may be other uses for the term PAGELETS, but this is what I heard from engineering sources when Alpha first appeared.