On 31.01.24 15:08, Michal Hocko wrote:
On Wed 31-01-24 10:26:13, Ryan Roberts wrote:
IIRC there is an option to zero memory when it is freed back to the buddy? So
that could be a place where time is proportional to size rather than
proportional to folio count? But I think that option is intended for debug only?
So perhaps not a problem in practice?
init_on_free is considered a security/hardening feature more than a
debugging one. It will surely add an overhead and I guess this is
something people who use it know about. The batch size limit is a latency
reduction feature for !PREEMPT kernels but by no means it should be
considered low latency guarantee feature. A lot of has changed since
the limit was introduced and the current latency numbers will surely be
different than back then. As long as soft lockups do not trigger again
this should be acceptable IMHO.
It could now be zeroing out ~512 MiB. That shouldn't take double-digit
seconds unless we are running in a very problematic environment
(over-committed VM). But then, we might have different problems already.
I'll do some sanity checks with an extremely large processes (as much as
I can fit on my machines), with a !CONFIG_PREEMPT kernel and
init_on_free, to see if anything pops up.
Thanks Michal!
--
Cheers,
David / dhildenb
