On Mon, Oct 16, 2023 at 03:19:22PM +0200, Jan Beulich wrote: > On 06.10.2023 17:27, Roger Pau Monné wrote: > > On Fri, Oct 06, 2023 at 04:09:19PM +0100, Julien Grall wrote: > >> On 06/10/2023 15:44, Andrew Cooper wrote: > >>> From: Alejandro Vallejo <alejandro.vall...@cloud.com> > >>> > >>> Adds a new compile-time flag to allow disabling PDX compression and > >>> compiles out compression-related code/data. It also shorts the pdx<->pfn > >>> conversion macros and creates stubs for masking functions. > >>> > >>> While at it, removes the old arch-defined CONFIG_HAS_PDX flag. Despite > >>> the > >>> illusion of choice, it was not optional. > >>> > >>> There are ARM and PPC platforms with sparse RAM banks - leave compression > >>> active by default there. OTOH, there are no known production x86 systems > >>> with > >>> sparse RAM banks, so disable compression. This decision can be revisited > >>> if > >>> such a platform comes along. > >> > >> (Process remarks rather than the code itself) > >> > >> Jan is away this week so I want to make sure this doesn't go in without him > >> having a say. > >> > >> While I don't particularly care about the approach taken for x86, Jan > >> voiced > >> concerned with this approach and so far I didn't see any conclusion. If > >> there is any, then please point me to them. > >> > >> For the record, the objections from Jan are in [1]. If we want to ignore > >> them, then I think we need a vote. Possibly only from the x86 folks (?). > > > > I would be fine in leaving the option to be selected if we knew that > > such x86 systems might be feasible, but so far we have seen 0 x86 > > systems with sparse RAM. That said, I don't have a strong opinion, but > > the hiding on x86 seems fine to me. Interested parties can always > > forcefully select the option, and a case can be made to make it > > available again on Kconfig. > > I find it odd to demand people to change source code for aspects like > this. The very least I'd expect is that BIGMEM configurations (which > I've never seen any production use of) can actually also engage PDX.
So we expect BIGMEM to have sparse RAM regions? I would have expected systems with >16TB of RAM to still be contiguous. Thanks, Roger.
