linux-kernel - Re: [PATCH] mm: evict streaming IO cache first

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Message-Id: <20081117153012.51ece88f.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 17 Nov 2008 15:30:12 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Gene Heskett <gene.heskett@...il.com>
Subject: Re: [PATCH] mm: evict streaming IO cache first

On Sun, 16 Nov 2008 20:47:20 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Sun, 16 Nov 2008 16:20:26 -0500 Rik van Riel <riel@...hat.com> wrote:
> Anyway, we need to do something.
> 
> Shouldn't get_scan_ratio() be handling this case already?
> 
Hmm, could I make a question ?

I think

  - recent_rolated[LRU_FILE] is incremented when file cache is moved from
    ACTIVE_FILE to INACTIVE_FILE.
  - recent_scanned[LRU_FILE] is sum of scanning numbers on INACTIVE/ACTIVE list
    of file.
  - file caches are added to INACITVE_FILE, at first.
  - get_scan_ratio() calculates %file to be

                         file        recent rotated.
   %file = IO_cost * ------------ / -------------
                      anon + file    recent scanned.

But when "files are used by streaming or some touch once application",
there is no rotation because they are in INACTIVE FILE at first add_to_lru().
But recent_rotated will not increase while recent_scanned goes bigger and bigger.

Then %file goes to 0 rapidly.

Hmm?

Thanks,
-kame

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