On 2020-02-03 12:27, Vijayanand Jitta wrote:
On 1/30/2020 11:58 PM, Christopher Lameter wrote:
On Thu, 30 Jan 2020, vjitta@xxxxxxxxxxxxxx wrote:
Random sequence cache is precomputed during slab object creation
based up on the object size and no of objects per slab. These could
be changed when flags like SLAB_STORE_USER, SLAB_POISON are updated
from sysfs. So when shuffle_freelist is called during slab_alloc it
Sorry no. That cannot happen. Changing the size of the slab is only
possible if no slab pages are allocated. Any sysfs changes that affect
the
object size must fail if object and slab pages are already allocated.
If you were able to change the object size then we need to prevent
that
from happening.
Yes, size of slab can't be changed after objects are allocated, that
holds
true even with this change. Let me explain a bit more about the use
case here
ZRAM compression uses the slub allocator, by enabling the slub debug
flags like
SLAB_STORE_USER etc.. the memory consumption will rather be increased
which doesn't
serve the purpose of ZRAM compression. So, such flags are to be
disabled before the
allocations happen, this requires updation of random sequence cache as
object
size and number of objects change after these flags are disabled.
So, the sequence will be
1. Slab creation (this will set a precomputed random sequence cache)
2. Remove the debug flags
3. update the random sequence cache
4. Mount zram and then start using it for allocations.
Thanks,
Vijay
Waiting for your response.
Thanks,
Vijay
