On Wed, 10 Jul 2024, Vlastimil Babka wrote:
With this patch cgroup restrictions memory policies etc etc no longer work
in the slab allocator.
The only difference is memory policy from get_task_policy(), and the rest is
the same, right?
There are also the cpuset/cgroup restrictions via the zonelists that are
bypassed by removing alloc_pages()
But this only affects new slab page allocation, while getting objects from
existing slabs isn't subject to memory policies, so now it's at least
consistent? Do you have some use case where it matters?
Yes this means you cannot redirect kmalloc based kernel metadata
allocation when creating f.e. cgroups for another NUMA node. This affects
all kernel metadata allocation during syscalls that used to be
controllable via numa methods.
SLAB implemented memory allocations policies per object. SLUB moved that
to implement these policies only when allocating a page frame. If this
patch is left in then there wont be any support for memory allocation
policies left in the slab allocators.
We have some internal patches now that implement memory policies on a per
object basis for SLUB here.
This is a 10-15% regression on various benchmarks when objects like the
scheduler statistics structures are misplaced.
