You asked for an instruction to clear a page to zeros. I proposed an instruction to clear a page to zeros without causing an extraneous page-in if the page was previously paged out and without causing an unnecessary page out if the page was stolen after being cleared but before you wrote something new into it.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List [[email protected]] on behalf of Tom Harper [[email protected]] Sent: Thursday, April 14, 2022 3:46 PM To: [email protected] Subject: Re: Next instruction needed I don’t see what this has to do with what I’m proposing. Sent from my iPhone > On Apr 14, 2022, at 3:39 PM, Seymour J Metz <[email protected]> wrote: > > Not directly, but it also wouldn't prevent unnecessary page outs after page > steals. A better new instruction would be an unpriviled instruction similar > to IPTE; mark the page as invalid only if write is permitted, otherwise > protection exception. Maybe even a version that also clears the page and sets > a PTE that cause the next write to set it back to valid. The intent is to > cause the OS to treat the page as valid but unmodified since allocation, and > to avoid extraneous interrupts. > > > -- > Shmuel (Seymour J.) Metz > http://mason.gmu.edu/~smetz3 > > ________________________________________ > From: IBM Mainframe Assembler List [[email protected]] on > behalf of Paul Gilmartin [[email protected]] > Sent: Thursday, April 14, 2022 1:26 PM > To: [email protected] > Subject: Re: Next instruction needed > >> On Apr 14, 2022, at 11:06:09, Tom Harper wrote: >> >> IMHO, the next instruction to add to z/Architecture would be an instruction >> to clear storage to zeros. >> > Would that cause a Lot of paging I/O? Would it be better to mark all pages as > invalid, to be cleared automatically when referenced, if ever? > > That would be an O/S function, not hardware. > > -- > gil -------------------------------------------------------------------------------- This e-mail message, including any attachments, appended messages and the information contained therein, is for the sole use of the intended recipient(s). If you are not an intended recipient or have otherwise received this email message in error, any use, dissemination, distribution, review, storage or copying of this e-mail message and the information contained therein is strictly prohibited. If you are not an intended recipient, please contact the sender by reply e-mail and destroy all copies of this email message and do not otherwise utilize or retain this email message or any or all of the information contained therein. Although this email message and any attachments or appended messages are believed to be free of any virus or other defect that might affect any computer system into which it is received and opened, it is the responsibility of the recipient to ensure that it is virus free and no responsibility is accepted by the sender for any loss or damage arising in any way from its opening or use.
