buffer_cache: Eliminate redundant map lookup in MarkRegionAsWritten()

We can make use of emplace()'s return value to determine whether or not
we need to perform an increment.

emplace() performs no insertion if an element already exist, so this can
eliminate a find() call.
This commit is contained in:
Lioncash 2020-07-20 17:40:04 -04:00
parent ad0b295125
commit 26c6c71837

View file

@ -524,11 +524,8 @@ private:
void MarkRegionAsWritten(VAddr start, VAddr end) {
const u64 page_end = end >> WRITE_PAGE_BIT;
for (u64 page_start = start >> WRITE_PAGE_BIT; page_start <= page_end; ++page_start) {
auto it = written_pages.find(page_start);
if (it != written_pages.end()) {
it->second = it->second + 1;
} else {
written_pages.insert_or_assign(page_start, 1);
if (const auto [it, inserted] = written_pages.emplace(page_start, 1); !inserted) {
++it->second;
}
}
}
@ -539,7 +536,7 @@ private:
auto it = written_pages.find(page_start);
if (it != written_pages.end()) {
if (it->second > 1) {
it->second = it->second - 1;
--it->second;
} else {
written_pages.erase(it);
}