[PATCH v3] mm: make minimum slab alignment a runtime property

[Catalin Marinas]

On Fri, Apr 22, 2022 at 01:18:30PM -0700, Peter Collingbourne wrote:
> When CONFIG_KASAN_HW_TAGS is enabled we currently increase the minimum
> slab alignment to 16. This happens even if MTE is not supported in
> hardware or disabled via kasan=off, which creates an unnecessary
> memory overhead in those cases. Eliminate this overhead by making
> the minimum slab alignment a runtime property and only aligning to
> 16 if KASAN is enabled at runtime.
> 
> On a DragonBoard 845c (non-MTE hardware) with a kernel built with
> CONFIG_KASAN_HW_TAGS, waiting for quiescence after a full Android
> boot I see the following Slab measurements in /proc/meminfo (median
> of 3 reboots):
> 
> Before: 169020 kB
> After:  167304 kB
> 
> Link: https://linux-review.googlesource.com/id/I752e725179b43b144153f4b6f584ceb646473ead
> Signed-off-by: Peter Collingbourne <pcc at google.com>
> Reviewed-by: Andrey Konovalov <andreyknvl at gmail.com>

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>