[PATCH 1/5] mm: Kconfig: move swap and slab config options to the MM section

Johannes Weiner
2022-04-27T16:00:12Z

These are currently under General Setup. MM seems like a better fit.

Signed-off-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
---
init/Kconfig | 123 ---------------------------------------------------
mm/Kconfig | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 123 insertions(+), 123 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 4489416f1e5c..468fe27cec0b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -375,23 +375,6 @@ config DEFAULT_HOSTNAME
but you may wish to use a different default here to make a minimal
system more usable with less configuration.

-#
-# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
-# add proper SWAP support to them, in which case this can be remove.
-#
-config ARCH_NO_SWAP
- bool
-
-config SWAP
- bool "Support for paging of anonymous memory (swap)"
- depends on MMU && BLOCK && !ARCH_NO_SWAP
- default y
- help
- This option allows you to choose whether you want to have support
- for so called swap devices or swap files in your kernel that are
- used to provide more virtual memory than the actual RAM present
- in your computer. If unsure say Y.
-
config SYSVIPC
bool "System V IPC"
help
@@ -1909,112 +1892,6 @@ config COMPAT_BRK

On non-ancient distros (post-2000 ones) N is usually a safe choice.

-choice
- prompt "Choose SLAB allocator"
- default SLUB
- help
- This option allows to select a slab allocator.
-
-config SLAB
- bool "SLAB"
- depends on !PREEMPT_RT
- select HAVE_HARDENED_USERCOPY_ALLOCATOR
- help
- The regular slab allocator that is established and known to work
- well in all environments. It organizes cache hot objects in
- per cpu and per node queues.
-
-config SLUB
- bool "SLUB (Unqueued Allocator)"
- select HAVE_HARDENED_USERCOPY_ALLOCATOR
- help
- SLUB is a slab allocator that minimizes cache line usage
- instead of managing queues of cached objects (SLAB approach).
- Per cpu caching is realized using slabs of objects instead
- of queues of objects. SLUB can use memory efficiently
- and has enhanced diagnostics. SLUB is the default choice for
- a slab allocator.
-
-config SLOB
- depends on EXPERT
- bool "SLOB (Simple Allocator)"
- depends on !PREEMPT_RT
- help
- SLOB replaces the stock allocator with a drastically simpler
- allocator. SLOB is generally more space efficient but
- does not perform as well on large systems.
-
-endchoice
-
-config SLAB_MERGE_DEFAULT
- bool "Allow slab caches to be merged"
- default y
- depends on SLAB || SLUB
- help
- For reduced kernel memory fragmentation, slab caches can be
- merged when they share the same size and other characteristics.
- This carries a risk of kernel heap overflows being able to
- overwrite objects from merged caches (and more easily control
- cache layout), which makes such heap attacks easier to exploit
- by attackers. By keeping caches unmerged, these kinds of exploits
- can usually only damage objects in the same cache. To disable
- merging at runtime, "slab_nomerge" can be passed on the kernel
- command line.
-
-config SLAB_FREELIST_RANDOM
- bool "Randomize slab freelist"
- depends on SLAB || SLUB
- help
- Randomizes the freelist order used on creating new pages. This
- security feature reduces the predictability of the kernel slab
- allocator against heap overflows.
-
-config SLAB_FREELIST_HARDENED
- bool "Harden slab freelist metadata"
- depends on SLAB || SLUB
- help
- Many kernel heap attacks try to target slab cache metadata and
- other infrastructure. This options makes minor performance
- sacrifices to harden the kernel slab allocator against common
- freelist exploit methods. Some slab implementations have more
- sanity-checking than others. This option is most effective with
- CONFIG_SLUB.
-
-config SHUFFLE_PAGE_ALLOCATOR
- bool "Page allocator randomization"
- default SLAB_FREELIST_RANDOM && ACPI_NUMA
- help
- Randomization of the page allocator improves the average
- utilization of a direct-mapped memory-side-cache. See section
- 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
- 6.2a specification for an example of how a platform advertises
- the presence of a memory-side-cache. There are also incidental
- security benefits as it reduces the predictability of page
- allocations to compliment SLAB_FREELIST_RANDOM, but the
- default granularity of shuffling on the "MAX_ORDER - 1" i.e,
- 10th order of pages is selected based on cache utilization
- benefits on x86.
-
- While the randomization improves cache utilization it may
- negatively impact workloads on platforms without a cache. For
- this reason, by default, the randomization is enabled only
- after runtime detection of a direct-mapped memory-side-cache.
- Otherwise, the randomization may be force enabled with the
- 'page_alloc.shuffle' kernel command line parameter.
-
- Say Y if unsure.
-
-config SLUB_CPU_PARTIAL
- default y
- depends on SLUB && SMP
- bool "SLUB per cpu partial cache"
- help
- Per cpu partial caches accelerate objects allocation and freeing
- that is local to a processor at the price of more indeterminism
- in the latency of the free. On overflow these caches will be cleared
- which requires the taking of locks that may cause latency spikes.
- Typically one would choose no for a realtime system.
-
config MMAP_ALLOW_UNINITIALIZED
bool "Allow mmapped anonymous memory to be uninitialized"
depends on EXPERT && !MMU
diff --git a/mm/Kconfig b/mm/Kconfig
index c2141dd639e3..675a6be43739 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -2,6 +2,129 @@

menu "Memory Management options"

+#
+# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
+# add proper SWAP support to them, in which case this can be remove.
+#
+config ARCH_NO_SWAP
+ bool
+
+config SWAP
+ bool "Support for paging of anonymous memory (swap)"
+ depends on MMU && BLOCK && !ARCH_NO_SWAP
+ default y
+ help
+ This option allows you to choose whether you want to have support
+ for so called swap devices or swap files in your kernel that are
+ used to provide more virtual memory than the actual RAM present
+ in your computer. If unsure say Y.
+
+choice
+ prompt "Choose SLAB allocator"
+ default SLUB
+ help
+ This option allows to select a slab allocator.
+
+config SLAB
+ bool "SLAB"
+ depends on !PREEMPT_RT
+ select HAVE_HARDENED_USERCOPY_ALLOCATOR
+ help
+ The regular slab allocator that is established and known to work
+ well in all environments. It organizes cache hot objects in
+ per cpu and per node queues.
+
+config SLUB
+ bool "SLUB (Unqueued Allocator)"
+ select HAVE_HARDENED_USERCOPY_ALLOCATOR
+ help
+ SLUB is a slab allocator that minimizes cache line usage
+ instead of managing queues of cached objects (SLAB approach).
+ Per cpu caching is realized using slabs of objects instead
+ of queues of objects. SLUB can use memory efficiently
+ and has enhanced diagnostics. SLUB is the default choice for
+ a slab allocator.
+
+config SLOB
+ depends on EXPERT
+ bool "SLOB (Simple Allocator)"
+ depends on !PREEMPT_RT
+ help
+ SLOB replaces the stock allocator with a drastically simpler
+ allocator. SLOB is generally more space efficient but
+ does not perform as well on large systems.
+
+endchoice
+
+config SLAB_MERGE_DEFAULT
+ bool "Allow slab caches to be merged"
+ default y
+ depends on SLAB || SLUB
+ help
+ For reduced kernel memory fragmentation, slab caches can be
+ merged when they share the same size and other characteristics.
+ This carries a risk of kernel heap overflows being able to
+ overwrite objects from merged caches (and more easily control
+ cache layout), which makes such heap attacks easier to exploit
+ by attackers. By keeping caches unmerged, these kinds of exploits
+ can usually only damage objects in the same cache. To disable
+ merging at runtime, "slab_nomerge" can be passed on the kernel
+ command line.
+
+config SLAB_FREELIST_RANDOM
+ bool "Randomize slab freelist"
+ depends on SLAB || SLUB
+ help
+ Randomizes the freelist order used on creating new pages. This
+ security feature reduces the predictability of the kernel slab
+ allocator against heap overflows.
+
+config SLAB_FREELIST_HARDENED
+ bool "Harden slab freelist metadata"
+ depends on SLAB || SLUB
+ help
+ Many kernel heap attacks try to target slab cache metadata and
+ other infrastructure. This options makes minor performance
+ sacrifices to harden the kernel slab allocator against common
+ freelist exploit methods. Some slab implementations have more
+ sanity-checking than others. This option is most effective with
+ CONFIG_SLUB.
+
+config SHUFFLE_PAGE_ALLOCATOR
+ bool "Page allocator randomization"
+ default SLAB_FREELIST_RANDOM && ACPI_NUMA
+ help
+ Randomization of the page allocator improves the average
+ utilization of a direct-mapped memory-side-cache. See section
+ 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
+ 6.2a specification for an example of how a platform advertises
+ the presence of a memory-side-cache. There are also incidental
+ security benefits as it reduces the predictability of page
+ allocations to compliment SLAB_FREELIST_RANDOM, but the
+ default granularity of shuffling on the "MAX_ORDER - 1" i.e,
+ 10th order of pages is selected based on cache utilization
+ benefits on x86.
+
+ While the randomization improves cache utilization it may
+ negatively impact workloads on platforms without a cache. For
+ this reason, by default, the randomization is enabled only
+ after runtime detection of a direct-mapped memory-side-cache.
+ Otherwise, the randomization may be force enabled with the
+ 'page_alloc.shuffle' kernel command line parameter.
+
+ Say Y if unsure.
+
+config SLUB_CPU_PARTIAL
+ default y
+ depends on SLUB && SMP
+ bool "SLUB per cpu partial cache"
+ help
+ Per cpu partial caches accelerate objects allocation and freeing
+ that is local to a processor at the price of more indeterminism
+ in the latency of the free. On overflow these caches will be cleared
+ which requires the taking of locks that may cause latency spikes.
+ Typically one would choose no for a realtime system.
+
config SELECT_MEMORY_MODEL
def_bool y
depends on ARCH_SELECT_MEMORY_MODEL
--
2.35.3