Re: Problem in Page Cache Replacement

On 11/22/2012 11:53 PM, Fengguang Wu wrote:

On Thu, Nov 22, 2012 at 11:41:07PM +0800, Fengguang Wu wrote:

quoted

On Wed, Nov 21, 2012 at 12:07:22PM +0200, Metin DA?A?lA 1/4  wrote:

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On Wed, Nov 21, 2012 at 12:00 PM, Jaegeuk Hanse [off-list ref] wrote:

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On 11/21/2012 05:58 PM, metin d wrote:

Hi Fengguang,

I run tests and attached the results. The line below I guess shows the data-1 page caches.

0x000000080000006c       6584051    25718  __RU_lA___________________P________    referenced,uptodate,lru,active,private


I thinks this is just one state of page cache pages.

But why these page caches are in this state as opposed to other page
caches. From the results I conclude that:

data-1 pages are in state : referenced,uptodate,lru,active,private

I wonder if it's this code that stops data-1 pages from being
reclaimed:

shrink_page_list():

                 if (page_has_private(page)) {
                         if (!try_to_release_page(page, sc->gfp_mask))
                                 goto activate_locked;

What's the filesystem used?

Ah it's more likely caused by this logic:

         if (is_active_lru(lru)) {
                 if (inactive_list_is_low(mz, file))
                         shrink_active_list(nr_to_scan, mz, sc, priority, file);

The active file list won't be scanned at all if it's smaller than the
active list. In this case, it's inactive=33586MB > active=25719MB. So
the data-1 pages in the active list will never be scanned and reclaimed.

Hi Fengguang,

It seems that most of data-1 file pages are in active lru cache and most 
of data-2 file pages are in inactive lru cache. As Johannes mentioned, 
if inter-reference distance is bigger than half of memory, the pages 
will not be actived. How you intend to resolve this issue? Is Johannes's 
inactive list threshing idea  available?

Regards,
Jaegeuk

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quoted

data-2 pages are in state : referenced,uptodate,lru,mappedtodisk

Thanks,
Fengguang

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