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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.