[PATCH] docs: Add overview and SLUB allocator sections to slab documentation

[Nick Huang]

- Add "Overview" section explaining the slab allocator's role and purpose
- Document the three main slab allocator implementations (SLAB, SLUB, SLOB)
- Highlight SLUB as the default allocator on modern systems
- Add "SLUB Allocator" subsection with detailed information:
- Explain SLUB's design goals and advantages over legacy SLAB
- Document its focus on simplification and performance
- Note support for both uniprocessor and SMP systems

Signed-off-by: Nick Huang <sef1548@xxxxxxxxx>
---
 Documentation/mm/slab.rst | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Documentation/mm/slab.rst b/Documentation/mm/slab.rst
index 2bcc58ada302..2d1d093afb7b 100644
--- a/Documentation/mm/slab.rst
+++ b/Documentation/mm/slab.rst
@@ -4,6 +4,32 @@
 Slab Allocation
 ===============
 
+Overview
+========
+
+The slab allocator is responsible for efficient allocation and reuse of
+small kernel objects. It reduces internal fragmentation and improves
+performance by caching frequently used objects.
+
+The Linux kernel provides multiple slab allocator implementations,
+including SLAB, SLUB, and SLOB. Among these, SLUB is the default
+allocator on most modern systems.
+
+SLUB Allocator
+==============
+
+Overview
+--------
+
+SLUB is a slab allocator designed to replace the legacy SLAB allocator
+(mm/slab.c). It addresses the complexity, scalability limitations, and
+memory overhead of the SLAB implementation.
+
+The primary goal of SLUB is to simplify slab allocation while improving
+performance on both uniprocessor (UP) and symmetric multiprocessing (SMP)
+systems.
+
+
 Functions and structures
 ========================
 
-- 
2.43.0