linux-kernel - Re: [PATCH V4 3/6] mm: move MADV_FREE pages into LRU_INACTIVE

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Date:   Fri, 24 Feb 2017 10:49:39 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Shaohua Li <shli@...com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Kernel-team@...com, mhocko@...e.com, hughd@...gle.com,
        hannes@...xchg.org, riel@...hat.com, mgorman@...hsingularity.net,
        akpm@...ux-foundation.org
Subject: Re: [PATCH V4 3/6] mm: move MADV_FREE pages into LRU_INACTIVE_FILE
 list

On Wed, Feb 22, 2017 at 10:50:41AM -0800, Shaohua Li wrote:
> madv MADV_FREE indicate pages are 'lazyfree'. They are still anonymous
> pages, but they can be freed without pageout. To destinguish them
> against normal anonymous pages, we clear their SwapBacked flag.
> 
> MADV_FREE pages could be freed without pageout, so they pretty much like
> used once file pages. For such pages, we'd like to reclaim them once
> there is memory pressure. Also it might be unfair reclaiming MADV_FREE
> pages always before used once file pages and we definitively want to
> reclaim the pages before other anonymous and file pages.
> 
> To speed up MADV_FREE pages reclaim, we put the pages into
> LRU_INACTIVE_FILE list. The rationale is LRU_INACTIVE_FILE list is tiny
> nowadays and should be full of used once file pages. Reclaiming
> MADV_FREE pages will not have much interfere of anonymous and active
> file pages. And the inactive file pages and MADV_FREE pages will be
> reclaimed according to their age, so we don't reclaim too many MADV_FREE
> pages too. Putting the MADV_FREE pages into LRU_INACTIVE_FILE_LIST also
> means we can reclaim the pages without swap support. This idea is
> suggested by Johannes.
> 
> This patch doesn't move MADV_FREE pages to LRU_INACTIVE_FILE list yet to
> avoid bisect failure, next patch will do it.
> 
> The patch is based on Minchan's original patch.
> 
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Suggested-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Shaohua Li <shli@...com>

Other than that Johannes pointed out, code itself looks good to me.
However, I hope to merge this patch with next one.
It's enough simple to merge, change behavior(about deactivation),
mark_page_lazyfree is introduced but there is no callsite to use it
in this patch.

I don't think it's worth to separate.