Re: 答复: [PATCH] reusing of mapping page supplies a way for file page allocation under low memory due to pagecache over size and is controlled by sysctl parameters. it is used only for rw page allocation rather than fault or readahead allocation. it is like...

On Tue 31-05-16 13:35:37, zhouxianrong wrote:

Hey :
the consideration of this patch is that reusing mapping page
rather than allocating a new page for page cache when system be
placed in some states.  For lookup pages quickly add a new tag
PAGECACHE_TAG_REUSE for radix tree which tag the pages that is
suitable for reusing.

A page suitable for reusing within mapping is
1. clean
2. map count is zero
3. whose mapping is evictable

Those pages are trivially reclaimable so why should we tag them in a
special way?

[...]

How to startup the functional
1. the system is under low memory state and there are fs rw operations
2. page cache size is get bigger over sysctl limit

So is this a form of a page cache limit to trigger the reclaim earlier
than on the global memory pressure?
-- 
Michal Hocko
SUSE Labs

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