linux-kernel - Why isn't shrink_slab more zone oriented ?

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Message-ID: <CAFPAmTRHFOT+tc=J-=jTBpvi8ksnp6H32UsEwptrrv=hagjUsA@mail.gmail.com>
Date:	Mon, 26 Sep 2011 17:21:12 +0530
From:	"kautuk.c @samsung.com" <consul.kautuk@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Why isn't shrink_slab more zone oriented ?

Hi,

I was going through the do_try_to_free_pages(), balance_pgdat(),
__zone_reclaim()
functions and I see that shrink_zone and shrink_slab are called for each zone.

But, shrink_slab() doesn't seem to bother about the zone from where it
is freeing
memory.

My questions are:

- Will this be a strain on the direct/indirect reclamation algorithm ?
  The loops involved expects to free something from that particular zone.
  shrink_slab might take more time than is required to free up pages from that
  particular zone which might not be optimal.
  Am I right about this conclusion ?

- If the above is correct, then is there any work happening on this
front, i.e., to
  make shrink_slab functionality and the shrinker callbacks more zone-centric ?
  Are there any patches that I could look at or download from
somewhere for this ?

- Are there any other considerations to be careful of for making
shrink_slab more
  zone centric ? Can there be other side effects that affects
performance if the
  shrink_slab and shrinker callbacks are made to free pages only from
a particular
  zone ?

Thanks,
Kautuk.
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