Re: [PATCH] __isolate_lru_page: skip unneeded mode check

[Bob Liu <lliubbo@gmail.com>]

On 3/31/10, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> 2010/3/31 Bob Liu <lliubbo@gmail.com>:
>> From: Bob Liu <lliubbo@gmail.com>
>>
>> Whether mode is ISOLATE_BOTH or not, we should compare
>> page_is_file_cache with argument file.
>>
>> And there is no more need not when checking the active state.
>>
>> Signed-off-by: Bob Liu <lliubbo@gmail.com>
>> ---
>>  mm/vmscan.c |    9 ++-------
>>  1 files changed, 2 insertions(+), 7 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index e0e5f15..34d7e3d 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -862,15 +862,10 @@ int __isolate_lru_page(struct page *page, int mode,
>> int file)
>>        if (!PageLRU(page))
>>                return ret;
>>
>> -       /*
>> -        * When checking the active state, we need to be sure we are
>> -        * dealing with comparible boolean values.  Take the logical not
>> -        * of each.
>> -        */
>> -       if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
>> +       if (mode != ISOLATE_BOTH && (PageActive(page) != mode))
>>                return ret;
>
> no. please read the comment.
>

Hm,. I have read it, but still miss it :-).
PageActive(page) will return an int 0 or 1, mode is also int 0 or 1(
already != ISOLATE_BOTH).
There are comparible and why must to be sure to boolean values?

>> -       if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
>> +       if (page_is_file_cache(page) != file)
>>                return ret;
>
> no. please consider lumpy reclaim.
>

During lumpy reclaim mode is ISOLATE_BOTH, that case we don't check
page_is_file_cache() ?  Would you please explain it a little more ,i
am still unclear about it.
Thanks a lot.
-- 
Regards,
--Bob

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