linux-kernel - Re: [PATCH -mm 2/2] mm: vmscan: init reclaim_state in do_try_to_free

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Date:	Tue, 13 Jan 2015 10:55:57 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm 2/2] mm: vmscan: init reclaim_state in
 do_try_to_free_pages

On Mon, Jan 12, 2015 at 05:26:34PM -0500, Johannes Weiner wrote:
> On Mon, Jan 12, 2015 at 12:30:38PM +0300, Vladimir Davydov wrote:
> > All users of do_try_to_free_pages() want to have current->reclaim_state
> > set in order to account reclaimed slab pages. So instead of duplicating
> > the reclaim_state initialization code in each call site, let's do it
> > directly in do_try_to_free_pages().
> 
> Couldn't this be contained in shrink_slab() directly?

I had considered this possibility, but finally rejected it, because

 - some slab pages can be reclaimed from shrink_lruvec (e.g.
   buffer_head's); there shouldn't be too many of them though

 - struct reclaim_state looks to me as a generic placeholder for lots of
   reclaim-related stuff, though currently it is only used for counting
   reclaimed slab pages, so IMO it should be initialized before starting
   reclaim

Both arguments are not rock-solid as you can see, so if you think we can
neglect them, I'll do.

Thanks,
Vladimir
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