Commit ce7e9fae authored Nov 20, 2007 by Christian Borntraeger Committed by Martin Schwidefsky Nov 20, 2007

[S390] Optimize storage key handling for anonymous pages

page_mkclean used to call page_clear_dirty for every given page. This
is different to all other architectures, where the dirty bit in the
PTEs is only resetted, if page_mapping() returns a non-NULL pointer.
We can move the page_test_dirty/page_clear_dirty sequence into the
2nd if to avoid unnecessary iske/sske sequences, which are expensive.

This change also helps kvm for s390 as the host must transfer the
dirty bit into the guest status bits. By moving the page_clear_dirty
operation into the 2nd if, the vm will only call page_clear_dirty
for pages where it walks the mapping anyway. There it calls
ptep_clear_flush for writable ptes, so we can transfer the dirty bit
to the guest.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent b8e7a54c

mm/rmap.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -471,13 +471,14 @@ int page_mkclean(struct page *page)

		if (page_mapped(page)) {
		struct address_space *mapping = page_mapping(page);
		if (mapping)
		if (mapping) {
		ret = page_mkclean_file(mapping, page);
		if (page_test_dirty(page)) {
		page_clear_dirty(page);
		ret = 1;
		}
		}
		}

		return ret;
		}

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