[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v3 0/4] Make PDX compression optional
Hi Jan, On 16/08/2023 10:43, Jan Beulich wrote: On 16.08.2023 11:36, Alejandro Vallejo wrote:On Tue, Aug 08, 2023 at 02:02:16PM +0100, Alejandro Vallejo wrote:Currently there's a CONFIG_HAS_PDX Kconfig option, but it's impossible to disable it because the whole codebase performs unconditional compression/decompression operations on addresses. This has the unfortunate side effect that systems without a need for compression still have to pay the performance impact of juggling bits on every pfn<->pdx conversion (this requires reading several global variables). This series attempts to: * Leave the state of pdx and pdx compression documented * Factor out compression so it _can_ be removed through Kconfig * Make it so compression is disabled on x86 and enabled on both Aarch32 and Aarch64 by default. Series summary: Patch 1 Moves hard-coded compression-related logic to helper functions Patch 2 Refactors all instances of regions being validated for pdx compression conformance so it's done through a helper Patch 3 Non-functional reorder in order to simplify the patch 8 diff Patch 4 Adds new Kconfig option to compile out PDX compression and removes the old CONFIG_HAS_PDX, as it was non removable Already committed: v1/patch 1 documents the current general understanding of the pdx concept and pdx compression in particular v1/patch 3 Marks the pdx compression globals as ro_after_init v2/patch 1 Documents the differences between arm32 and arm64 directmaps Alejandro Vallejo (4): mm: Factor out the pdx compression logic in ma/va converters mm/pdx: Standardize region validation wrt pdx compression pdx: Reorder pdx.[ch] pdx: Add CONFIG_PDX_COMPRESSION as a common Kconfig option@Jan: Just making sure, are you generally ok with this series as-is?Well, okay would be too strong; I still don't see why my runtime patching series isn't re-considered. Do you have a pointer to the series? I would be interested to have a look.That said... the problem with alt-patching is this is architectural specific. Right now, this seems to be a bit unnecessary given that we believe that virtually no-one will have a platform (I know we talked about a potential one...) where PDX is compressing. Cheers, -- Julien Grall
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