RE: [RFC][PATCH] avoid swapping out with swappiness==0

[Satoru Moriya <satoru.moriya@hds.com>]

Hi,

Sorry for my late reply.

On 04/04/2012 01:38 PM, KOSAKI Motohiro wrote:
> (4/3/12 4:25 AM), Jerome Marchand wrote:
>> On 04/02/2012 07:10 PM, KOSAKI Motohiro wrote:
>>> 2012/3/30 Satoru Moriya<satoru.moriya@hds.com>:
>>>> So the kernel reclaims pages like following.
>>>>
>>>> nr_free + nr_filebacked>= watermark_high: reclaim only filebacked pages
>>>> nr_free + nr_filebacked<   watermark_high: reclaim only anonymous pages
>>>
>>> How?
>>
>> get_scan_count() checks that case explicitly:
>>
>>     if (global_reclaim(sc)) {
>>         free  = zone_page_state(mz->zone, NR_FREE_PAGES);
>>         /* If we have very few page cache pages,
>>            force-scan anon pages. */
>>         if (unlikely(file + free<= high_wmark_pages(mz->zone))) {
>>             fraction[0] = 1;
>>             fraction[1] = 0;
>>             denominator = 1;
>>             goto out;
>>         }
>>     }
> 
> Eek. This is silly. Nowaday many people enabled THP and it increase zone watermark.
> so, high watermask is not good threshold anymore.

Ah yes, it is not so small now.
On 4GB server, without THP min_free_kbytes is 8113 but
with THP it is 67584.

How about using low watermark or min watermark?
Are they still big?

...or should we use other value? 

Regards,
Satoru