Re: [PATCH v16 00/13] support "task_isolation" mode

On Tue, 7 Nov 2017, Chris Metcalf wrote:

quoted

Presumably we have another context there were we may be able to call into
the cleanup code with interrupts enabled.

Right now for task isolation we run with interrupts enabled during the
initial sys_prctl() call, and call quiet_vmstat_sync() there, which currently
calls refresh_cpu_vm_stats(false).  In fact we could certainly pass "true"
there instead (and probably should) since we can handle dealing with
the pagesets at this time.  As we return to userspace we will test that
nothing surprising happened with vmstat; if so we jam an EAGAIN into
the syscall result value, but if not, we will be in userspace and won't need
to touch the vmstat counters until we next go back into the kernel.

If you do it too early and there is another page allocator action then it
may potentially repopulate the caches. Since this is only draining the
caches for remote node allocation it may be rare and not that important.