mm/swapping01: new testcase
swapping01 - first time swap use results in heavy swapping
This case is used for testing upstream commit: 50a1598.
The upstream commit fixed a issue on s390/x platform that heavy
swapping might occur in some condition, however since the patch
was quite general, this testcase will be run on all supported
platforms to ensure no regression been introduced.
Details of the upstream fix:
On x86 a page without a mapper is by definition not referenced / old.
The s390 architecture keeps the reference bit in the storage key and
the current code will check the storage key for page without a mapper.
This leads to an interesting effect: the first time an s390 system
needs to write pages to swap it only finds referenced pages. This
causes a lot of pages to get added and written to the swap device.
To avoid this behaviour change page_referenced to query the storage
key only if there is a mapper of the page.
Test Strategy:
Try to allocate memory which size is slightly larger than current
available memory. After allocation done, continue loop for a while
and calculate the used swap size. The used swap size should be small
enough, else it indicates that heavy swapping is occured unexpectedly.
Signed-off-by: Caspar Zhang <caspar@casparzhang.com>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
3 files changed