Re: [PATCH 1/12] memcg avoid accounting special mappings not on LRU

[Balbir Singh <balbir@linux.vnet.ibm.com>]

KAMEZAWA Hiroyuki wrote:
> There are not-on-LRU pages which can be mapped and they are not worth to
> be accounted. (becasue we can't shrink them and need dirty codes to handle
> specical case) We'd like to make use of usual objrmap/radix-tree's protcol
> and don't want to account out-of-vm's control pages.
> 
> When special_mapping_fault() is called, page->mapping is tend to be NULL 
> and it's charged as Anonymous page.
> insert_page() also handles some special pages from drivers.
> 
> This patch is for avoiding to account special pages.
> 

Hmm... I am a little concerned that with these changes actual usage will much
more than what we report in memory.usage_in_bytes. Why not move them to
non-reclaimable LRU list as unevictable pages (once those patches go in, we can
push this as well). I suspect the size of special pages is too short to affect
anything or are you seeing something very different?
-- 
	Balbir