[PATCH RFC 00/10] KFENCE: A low-overhead sampling-based memory safety error detector

[Dave Hansen]

On 9/7/20 6:40 AM, Marco Elver wrote:
> KFENCE is designed to be enabled in production kernels, and has near
> zero performance overhead. Compared to KASAN, KFENCE trades performance
> for precision. 

Could you talk a little bit about where you expect folks to continue to
use KASAN?  How would a developer or a tester choose which one to use?

> KFENCE objects each reside on a dedicated page, at either the left or
> right page boundaries. The pages to the left and right of the object
> page are "guard pages", whose attributes are changed to a protected
> state, and cause page faults on any attempted access to them. Such page
> faults are then intercepted by KFENCE, which handles the fault
> gracefully by reporting a memory access error.

How much memory overhead does this end up having?  I know it depends on
the object size and so forth.  But, could you give some real-world
examples of memory consumption?  Also, what's the worst case?  Say I
have a ton of worst-case-sized (32b) slab objects.  Will I notice?