On 10.07.2023 18:12, Alejandro Vallejo wrote: > On Mon, Jul 10, 2023 at 09:43:34AM +0200, Jan Beulich wrote: >> This is ... >>>>> [snip] >>>>> + * This is where compression becomes useful. The idea is to note that if >>>>> + * you have several big chunks of memory sufficiently far apart you can >>>>> + * ignore the middle part of the address because it will always contain >>>>> + * zeroes as long as the base address is sufficiently well aligned and >>>>> the >>>>> + * length of the region is much smaller than the base address. >>>> >>>> As per above alignment of the base address doesn't really matter. >>> Where above? >> >> ... what "above" here meant. >> >>> As far as I understand you need enough alignment to cover the >>> hole or you won't have zeroes to compress. Point in case: >>> >>> * region1: [0x0000000000000000 - >>> 0x00000000FFFFFFFF] >>> >>> * region2: [0x0001FFFFFFFFF000 - >>> 0x00020000FFFFFFFF] >>> >>> I can agree this configuration is beyond dumb and statistically unlikely to >>> exist in the wild, but it should (IMO) still be covered by that comment. >> >> Right, but this isn't relevant here - in such a case no compression >> can occur, yes, but not (just) because of missing alignment. See the >> example I gave above (in the earlier reply) for where alignment >> clearly doesn't matter for compression to be possible. >> >> Jan > Fair enough. Then I think we can simply drop the last sentence and be done > with it. > > So the paragraph becomes: > ``` > * This is where compression becomes useful. The idea is to note that if > * you have several big chunks of memory sufficiently far apart you can > * ignore the middle part of the address because it will always contain > * zeroes. > ``` > The details on when or how compression is possible are implicit in the > following example anyway. > > Would that, combined with v3, take care of everything?
I'm yet to look at v3. Sorry, too many things going on / pending. Jan
