On 2/1/19 6:15 AM, Dan Williams wrote: > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1714,6 +1714,29 @@ config SLAB_FREELIST_HARDENED > sacrifies to harden the kernel slab allocator against common > freelist exploit methods. > > +config SHUFFLE_PAGE_ALLOCATOR > + bool "Page allocator randomization" > + default SLAB_FREELIST_RANDOM && ACPI_NUMA > + help > + Randomization of the page allocator improves the average > + utilization of a direct-mapped memory-side-cache. See section > + 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI > + 6.2a specification for an example of how a platform advertises > + the presence of a memory-side-cache. There are also incidental > + security benefits as it reduces the predictability of page > + allocations to compliment SLAB_FREELIST_RANDOM, but the > + default granularity of shuffling on 4MB (MAX_ORDER) pages is > + selected based on cache utilization benefits. > + > + While the randomization improves cache utilization it may > + negatively impact workloads on platforms without a cache. For > + this reason, by default, the randomization is enabled only > + after runtime detection of a direct-mapped memory-side-cache. > + Otherwise, the randomization may be force enabled with the > + 'page_alloc.shuffle' kernel command line parameter. > + > + Say Y if unsure. It says "Say Y if unsure", yet if I run make oldconfig, the default is N. Does that make sense? > Page allocator randomization (SHUFFLE_PAGE_ALLOCATOR) [N/y/?] (NEW)
