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authorIngo Molnar <mingo@kernel.org>2021-11-11 07:32:33 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-11 20:34:35 +0300
commit252220dab9d4e4aa61f87b729468e8ac68fcc8bb (patch)
tree6166c538306d56d00065b19369261818a52bf137
parent0093de693fe7baf31641d1863793e6db93a43b6e (diff)
downloadlinux-252220dab9d4e4aa61f87b729468e8ac68fcc8bb.tar.xz
mm: allow only SLUB on PREEMPT_RT
Memory allocators may disable interrupts or preemption as part of the allocation and freeing process. For PREEMPT_RT it is important that these sections remain deterministic and short and therefore don't depend on the size of the memory to allocate/ free or the inner state of the algorithm. Until v3.12-RT the SLAB allocator was an option but involved several changes to meet all the requirements. The SLUB design fits better with PREEMPT_RT model and so the SLAB patches were dropped in the 3.12-RT patchset. Comparing the two allocator, SLUB outperformed SLAB in both throughput (time needed to allocate and free memory) and the maximal latency of the system measured with cyclictest during hackbench. SLOB was never evaluated since it was unlikely that it preforms better than SLAB. During a quick test, the kernel crashed with SLOB enabled during boot. Disable SLAB and SLOB on PREEMPT_RT. [bigeasy@linutronix.de: commit description] Link: https://lkml.kernel.org/r/20211015210336.gen3tib33ig5q2md@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--init/Kconfig2
1 files changed, 2 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 21b1f4870c80..45bcaa8e7481 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1896,6 +1896,7 @@ choice
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
@@ -1916,6 +1917,7 @@ config SLUB
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