linux-kernel - Re: [v5][PATCH 5/6] mm: vmscan: batch shrink_page

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Message-ID: <20130604233229.GB31006@blaptop>
Date:	Wed, 5 Jun 2013 08:32:29 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Dave Hansen <dave@...1.net>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, mgorman@...e.de,
	tim.c.chen@...ux.intel.com
Subject: Re: [v5][PATCH 5/6] mm: vmscan: batch shrink_page_list() locking
 operations

On Tue, Jun 04, 2013 at 08:29:18AM -0700, Dave Hansen wrote:
> On 06/03/2013 11:02 PM, Minchan Kim wrote:
> >> > Why do we need new lru list instead of using @free_pages?
> > I got your point that @free_pages could have freed page by
> > put_page_testzero of shrink_page_list and they don't have
> > valid mapping so __remove_mapping_batch's mapping_release_page
> > would access NULL pointer.
> > 
> > I think it would be better to mention it in comment. :(
> > Otherwise, I suggest we can declare another new LIST_HEAD to
> > accumulate pages freed by put_page_testzero in shrink_page_list
> > so __remove_mapping_batch don't have to declare temporal LRU list
> > and can remove unnecessary list_move operation.
> 
> If I respin them again, I'll add a comment.

Thanks. it's enough for me.

> 
> I guess we could splice the whole list over at once instead of moving
> the pages individually.  But, what are we trying to optimize here?
> Saving a list_head worth of space on the stack?

Never mind. At first, I thought we can simply use @free_pages instead of
redundant new LRU list and it's *minor*. That's why I already gave
my Reviewed-by. But you woke up my brain so I realized it so I don't have
a concern any more about your patch.

Thanks.
-- 
Kind regards,
Minchan Kim
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