Re: [PATCH 0/3] kasan: hw_tags: some micro-optimizations

[Harry Yoo (Oracle)]

I have a few questions...

Does the performance of KASAN_HW_TAGS matter?

Yes, the performance of Hardware Tag-Based KASAN matters because
it is meant to be used in production on mobile devices as it utilizes
cutting-edge (to me) hardware support instead of compiler
instrumentation.

Do you have data or are you planning to measure the performance
impact of this work?

On Wed, May 13, 2026 at 04:27:31PM +0530, Dev Jain wrote:
> Patch 1 uses GFP_SKIP_KASAN to skip unpoisoning of a slab page in the page
> allocator, since slab allocator itself poisons the slab page immediately.

If __GFP_SKIP_KASAN skips unpoisoning, why should the slab allocator
poison the whole page (kasan_poison_slab())? It's already poisoned.

> Patch 2 and 3 remove wasted work while poisoning the tail end of the
> vmalloc/slab allocation.

> ---
> Based on 7.1-rc2.
> 
> Dev Jain (3):
>   mm/slub: hw_tags: skip page-allocator unpoisoning on slab allocation
>   kasan: avoid re-poisoning tag-based kmalloc redzones
>   vmalloc: hw_tags: optimize vmalloc redzoning
> 
>  include/linux/kasan.h | 17 +++++++++----
>  mm/kasan/common.c     | 55 +++++++++++++++++++++++++++++++++----------
>  mm/kasan/hw_tags.c    | 13 ++++++----
>  mm/page_alloc.c       |  2 +-
>  mm/slub.c             | 22 ++++++++++++-----
>  5 files changed, 79 insertions(+), 30 deletions(-)
> 
> -- 
> 2.43.0
> 

-- 
Cheers,
Harry / Hyeonggon