zsmalloc: make zspage chain size configurable

Remove hard coded limit on the maximum number of physical pages
per-zspage.

This will allow tuning of zsmalloc pool as zspage chain size changes
`pages per-zspage` and `objects per-zspage` characteristics of size
classes which also affects size classes clustering (the way size classes
are merged).

Link: https://lkml.kernel.org/r/20230118005210.2814763-4-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 39df30dcabe3..83b1d278b31c 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -191,6 +191,25 @@ config ZSMALLOC_STAT
 	  information to userspace via debugfs.
 	  If unsure, say N.
 
+config ZSMALLOC_CHAIN_SIZE
+	int "Maximum number of physical pages per-zspage"
+	default 4
+	range 4 16
+	depends on ZSMALLOC
+	help
+	  This option sets the upper limit on the number of physical pages
+	  that a zmalloc page (zspage) can consist of. The optimal zspage
+	  chain size is calculated for each size class during the
+	  initialization of the pool.
+
+	  Changing this option can alter the characteristics of size classes,
+	  such as the number of pages per zspage and the number of objects
+	  per zspage. This can also result in different configurations of
+	  the pool, as zsmalloc merges size classes with similar
+	  characteristics.
+
+	  For more information, see zsmalloc documentation.
+
 menu "SLAB allocator options"
 
 choice