Re: [LTP] [PATCH] mm/swapping01: new testcase

[Caspar Z. <ca...@ca...>]

On 10/18/2011 07:02 PM, Caspar Zhang wrote:
> 
> swapping01 - first time swap use results in heavy swapping
> 
> This case is used for testing upstream commit:
> 50a15981a1fac7e019ff7c3cba87531fb580f065
> 
> The upstream commit fixed a issue on s390 platform that heavy
> swapping might occur in some condition, however since the patch
> was quite general, this testcase will be run on all supported
> platform 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.
> 
> Test Prerequisites:
> Free swap sapce should be > COE_SLIGHT_OVER, else an oom-killer
> will be triggered.
> 
> Signed-off-by: Caspar Zhang <ca...@ca...>
> ---
>  runtest/mm                                 |    2 +
>  testcases/kernel/mem/swapping/Makefile     |   24 ++++
>  testcases/kernel/mem/swapping/swapping01.c |  200 ++++++++++++++++++++++++++++
>  3 files changed, 226 insertions(+), 0 deletions(-)
>  create mode 100644 testcases/kernel/mem/swapping/Makefile
>  create mode 100644 testcases/kernel/mem/swapping/swapping01.c
> 

Hi Cyril, please review this test, thanks.

Caspar