[S390] cio: reduce cpu utilization during device scan
Minimize calls to cpu intensive function get_subchannel_by_schid()
by introducing function for_each_subchannel_staged() which
temporarily caches the information about registered subchannels
in a bitmap.
Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 69d56c7..3b45bbe 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -51,6 +51,62 @@
return ret;
}
+struct cb_data {
+ void *data;
+ struct idset *set;
+ int (*fn_known_sch)(struct subchannel *, void *);
+ int (*fn_unknown_sch)(struct subchannel_id, void *);
+};
+
+static int call_fn_known_sch(struct device *dev, void *data)
+{
+ struct subchannel *sch = to_subchannel(dev);
+ struct cb_data *cb = data;
+ int rc = 0;
+
+ idset_sch_del(cb->set, sch->schid);
+ if (cb->fn_known_sch)
+ rc = cb->fn_known_sch(sch, cb->data);
+ return rc;
+}
+
+static int call_fn_unknown_sch(struct subchannel_id schid, void *data)
+{
+ struct cb_data *cb = data;
+ int rc = 0;
+
+ if (idset_sch_contains(cb->set, schid))
+ rc = cb->fn_unknown_sch(schid, cb->data);
+ return rc;
+}
+
+int for_each_subchannel_staged(int (*fn_known)(struct subchannel *, void *),
+ int (*fn_unknown)(struct subchannel_id,
+ void *), void *data)
+{
+ struct cb_data cb;
+ int rc;
+
+ cb.set = idset_sch_new();
+ if (!cb.set)
+ return -ENOMEM;
+ idset_fill(cb.set);
+ cb.data = data;
+ cb.fn_known_sch = fn_known;
+ cb.fn_unknown_sch = fn_unknown;
+ /* Process registered subchannels. */
+ rc = bus_for_each_dev(&css_bus_type, NULL, &cb, call_fn_known_sch);
+ if (rc)
+ goto out;
+ /* Process unregistered subchannels. */
+ if (fn_unknown)
+ rc = for_each_subchannel(call_fn_unknown_sch, &cb);
+out:
+ idset_free(cb.set);
+
+ return rc;
+}
+
static struct subchannel *
css_alloc_subchannel(struct subchannel_id schid)
{
@@ -402,20 +458,56 @@
return 0;
}
+static int slow_eval_known_fn(struct subchannel *sch, void *data)
+{
+ int eval;
+ int rc;
+
+ spin_lock_irq(&slow_subchannel_lock);
+ eval = idset_sch_contains(slow_subchannel_set, sch->schid);
+ idset_sch_del(slow_subchannel_set, sch->schid);
+ spin_unlock_irq(&slow_subchannel_lock);
+ if (eval) {
+ rc = css_evaluate_known_subchannel(sch, 1);
+ if (rc == -EAGAIN)
+ css_schedule_eval(sch->schid);
+ }
+ return 0;
+}
+
+static int slow_eval_unknown_fn(struct subchannel_id schid, void *data)
+{
+ int eval;
+ int rc = 0;
+
+ spin_lock_irq(&slow_subchannel_lock);
+ eval = idset_sch_contains(slow_subchannel_set, schid);
+ idset_sch_del(slow_subchannel_set, schid);
+ spin_unlock_irq(&slow_subchannel_lock);
+ if (eval) {
+ rc = css_evaluate_new_subchannel(schid, 1);
+ switch (rc) {
+ case -EAGAIN:
+ css_schedule_eval(schid);
+ rc = 0;
+ break;
+ case -ENXIO:
+ case -ENOMEM:
+ case -EIO:
+ /* These should abort looping */
+ break;
+ default:
+ rc = 0;
+ }
+ }
+ return rc;
+}
+
static void css_slow_path_func(struct work_struct *unused)
{
- struct subchannel_id schid;
-
CIO_TRACE_EVENT(4, "slowpath");
- spin_lock_irq(&slow_subchannel_lock);
- init_subchannel_id(&schid);
- while (idset_sch_get_first(slow_subchannel_set, &schid)) {
- idset_sch_del(slow_subchannel_set, schid);
- spin_unlock_irq(&slow_subchannel_lock);
- css_evaluate_subchannel(schid, 1);
- spin_lock_irq(&slow_subchannel_lock);
- }
- spin_unlock_irq(&slow_subchannel_lock);
+ for_each_subchannel_staged(slow_eval_known_fn, slow_eval_unknown_fn,
+ NULL);
}
static DECLARE_WORK(slow_path_work, css_slow_path_func);
@@ -444,7 +536,6 @@
/* Reprobe subchannel if unregistered. */
static int reprobe_subchannel(struct subchannel_id schid, void *data)
{
- struct subchannel *sch;
int ret;
CIO_MSG_EVENT(6, "cio: reprobe 0.%x.%04x\n",
@@ -452,13 +543,6 @@
if (need_reprobe)
return -EAGAIN;
- sch = get_subchannel_by_schid(schid);
- if (sch) {
- /* Already known. */
- put_device(&sch->dev);
- return 0;
- }
-
ret = css_probe_device(schid);
switch (ret) {
case 0:
@@ -486,7 +570,7 @@
/* Make sure initial subchannel scan is done. */
wait_event(ccw_device_init_wq,
atomic_read(&ccw_device_init_count) == 0);
- ret = for_each_subchannel(reprobe_subchannel, NULL);
+ ret = for_each_subchannel_staged(NULL, reprobe_subchannel, NULL);
CIO_MSG_EVENT(2, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,
need_reprobe);