Messages in this thread | | | Subject | Re: swap storage alignment and stride size | From | "Martin K. Petersen" <> | Date | Thu, 16 Dec 2010 18:46:41 -0500 |
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>>>>> "Hugh" == Hugh Dickins <hughd@google.com> writes:
>> You called it a "header page". Does that imply that it is page sized?
Hugh> Yes. (Rather a nuisance on a PowerPC system which sometimes uses Hugh> a kernel with 4k pages and sometimes a kernel with 64k pages.)
Ok.
>> Or will it cause pages written to a 4k-aligned swap device to be >> misaligned?
Hugh> No, the 4k-aligned remains 4k-aligned, of course. But if you Hugh> aligned your swap partition on, say, a 1MB boundary, and are Hugh> thinking of working in aligned 1MB blocks, then it may be awkward Hugh> that there's always this special 4k at the start (it could be Hugh> written back each time even though it hasn't changed, but it's Hugh> still an odd case).
Yeah, I got that. I just wanted to make sure that the header was not 32 bytes or something like that because that would be highly painful from an I/O alignment perspective.
-- Martin K. Petersen Oracle Linux Engineering
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