Commit 47d30674 authored Nov 26, 2013 by Peter Oberparleiter Committed by Martin Schwidefsky Dec 16, 2013

s390/css: Prevent unnecessary allocation in subchannel loop



Subchannel looping function for_each_subchannel_staged() allocates a
subchannel-ID-bitmap to efficiently iterate over the list of known
and unknown subchannels. Since this function is also used to iterate
over known-subchannels only, optimize that case by not requiring the
ID-bitmap allocation and falling back to simple bus_for_each_dev()
looping.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 175746eb

drivers/s390/cio/css.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -69,6 +69,7 @@ static int call_fn_known_sch(struct device dev, void data)
		struct cb_data *cb = data;
		int rc = 0;

		if (cb->set)
		idset_sch_del(cb->set, sch->schid);
		if (cb->fn_known_sch)
		rc = cb->fn_known_sch(sch, cb->data);
		@@ -115,6 +116,13 @@ int for_each_subchannel_staged(int (fn_known)(struct subchannel , void *),
		cb.fn_known_sch = fn_known;
		cb.fn_unknown_sch = fn_unknown;

		if (fn_known && !fn_unknown) {
		/* Skip idset allocation in case of known-only loop. */
		cb.set = NULL;
		return bus_for_each_dev(&css_bus_type, NULL, &cb,
		call_fn_known_sch);
		}

		cb.set = idset_sch_new();
		if (!cb.set)
		/* fall back to brute force scanning in case of oom */