I am viewing the source code of __release_region() in kernel/resource.c.
And I have one comment for the performance issue.
For example, we have a resource tree like this.
10-89
20-79
30-49
55-59
60-64
65-69
80-89
100-279
If the caller wants to release a region of [50,59], the original code will
execute four times in the for loop in the subtree of 20-79.
After changing the code below, it will execute two times instead.
By using the "git annotate", I see this code is committed by Linus as the
initial version. So don't get more information about why this code is written
in this way.
Maybe the case I thought will not happen in the real world?
Your comment is warmly welcome. :)
diff --git a/kernel/resource.c b/kernel/resource.c
index 8461aea..81525b4 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -931,7 +931,7 @@ void __release_region(struct resource *parent,
resource_size_t start,
for (;;) {
struct resource *res = *p;
- if (!res)
+ if (!res || res->start > start)
break;
if (res->start <= start && res->end >= end) {
if (!(res->flags & IORESOURCE_BUSY)) {
Wei Yang
Help You, Help Me