Hi Zaibo,

On Tue, Feb 25, 2020 at 11:30:05AM +0800, Xu Zaibo wrote:

quoted

+struct iopf_queue *
+iopf_queue_alloc(const char *name, iopf_queue_flush_t flush, void *cookie)
+{
+	struct iopf_queue *queue;
+
+	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
+	if (!queue)
+		return NULL;
+
+	/*
+	 * The WQ is unordered because the low-level handler enqueues faults by
+	 * group. PRI requests within a group have to be ordered, but once
+	 * that's dealt with, the high-level function can handle groups out of
+	 * order.
+	 */
+	queue->wq = alloc_workqueue("iopf_queue/%s", WQ_UNBOUND, 0, name);

Should this workqueue use 'WQ_HIGHPRI | WQ_UNBOUND' or some flags like this
to decrease the unexpected
latency of I/O PageFault here? Or maybe, workqueue will show an uncontrolled
latency, even in a busy system.

I'll investigate the effect of these flags. So far I've only run on
completely idle systems but it would be interesting to add some
workqueue-heavy load in my tests.

Thanks,
Jean

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