mm: Drain LRUs upon resume to userspace on nohz_full CPUs
LRU batching can be source of disturbances for isolated workloads
running in the userspace because it requires kernel worker to handle
that and that would preempt the said task. The primary source for such
disruption would be __lru_add_drain_all which could be triggered from
non-isolated CPUs.
Why would an isolated CPU have anything on the pcp cache? Many syscalls
allocate pages that might end there. A typical and unavoidable one would
be fork/exec leaving pages on the cache behind just waiting for somebody
to drain.
Address the problem by noting a batch has been added to the cache and
schedule draining upon return to userspace so the work is done while the
syscall is still executing and there are no suprises while the task runs
in the userspace where it doesn't want to be preempted.
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: linux-mm@kvack.org
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
4 files changed
