From d66d109d3c9c31f4c2140a5ac6ab486c53cb0156 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Mon, 13 May 2019 17:23:05 -0700 Subject: [PATCH] mm/Kconfig: update "Memory Model" help text The help describing the memory model selection is outdated. It still says that SPARSEMEM is experimental and DISCONTIGMEM is a preferred over SPARSEMEM. Update the help text for the relevant options: * add a generic help for the "Memory Model" prompt * add description for FLATMEM * reduce the description of DISCONTIGMEM and add a deprecation note * prefer SPARSEMEM over DISCONTIGMEM Link: http://lkml.kernel.org/r/1556188531-20728-1-git-send-email-rppt@linux.ibm.com Signed-off-by: Mike Rapoport Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 48 +++++++++++++++++++++++------------------------- 1 file changed, 23 insertions(+), 25 deletions(-) diff --git a/mm/Kconfig b/mm/Kconfig index c5124c2cb0b2..ee8d1f311858 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -11,23 +11,24 @@ choice default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT default FLATMEM_MANUAL + help + This option allows you to change some of the ways that + Linux manages its memory internally. Most users will + only have one option here selected by the architecture + configuration. This is normal. config FLATMEM_MANUAL bool "Flat Memory" depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE help - This option allows you to change some of the ways that - Linux manages its memory internally. Most users will - only have one option here: FLATMEM. This is normal - and a correct option. - - Some users of more advanced features like NUMA and - memory hotplug may have different options here. - DISCONTIGMEM is a more mature, better tested system, - but is incompatible with memory hotplug and may suffer - decreased performance over SPARSEMEM. If unsure between - "Sparse Memory" and "Discontiguous Memory", choose - "Discontiguous Memory". + This option is best suited for non-NUMA systems with + flat address space. The FLATMEM is the most efficient + system in terms of performance and resource consumption + and it is the best option for smaller systems. + + For systems that have holes in their physical address + spaces and for features like NUMA and memory hotplug, + choose "Sparse Memory" If unsure, choose this option (Flat Memory) over any other. @@ -38,29 +39,26 @@ config DISCONTIGMEM_MANUAL This option provides enhanced support for discontiguous memory systems, over FLATMEM. These systems have holes in their physical address spaces, and this option provides - more efficient handling of these holes. However, the vast - majority of hardware has quite flat address spaces, and - can have degraded performance from the extra overhead that - this option imposes. + more efficient handling of these holes. - Many NUMA configurations will have this as the only option. + Although "Discontiguous Memory" is still used by several + architectures, it is considered deprecated in favor of + "Sparse Memory". - If unsure, choose "Flat Memory" over this option. + If unsure, choose "Sparse Memory" over this option. config SPARSEMEM_MANUAL bool "Sparse Memory" depends on ARCH_SPARSEMEM_ENABLE help This will be the only option for some systems, including - memory hotplug systems. This is normal. + memory hot-plug systems. This is normal. - For many other systems, this will be an alternative to - "Discontiguous Memory". This option provides some potential - performance benefits, along with decreased code complexity, - but it is newer, and more experimental. + This option provides efficient support for systems with + holes is their physical address space and allows memory + hot-plug and hot-remove. - If unsure, choose "Discontiguous Memory" or "Flat Memory" - over this option. + If unsure, choose "Flat Memory" over this option. endchoice -- 2.39.5