linux-kernel - Re: [PATCH -V2] mm: Add PageLayzyFree() helper functions for MADV

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Message-ID: <alpine.DEB.2.21.2003041243100.260792@chino.kir.corp.google.com>
Date:   Wed, 4 Mar 2020 12:45:27 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     David Hildenbrand <david@...hat.com>
cc:     "Huang, Ying" <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Zi Yan <ziy@...dia.com>, Michal Hocko <mhocko@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Minchan Kim <minchan@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH -V2] mm: Add PageLayzyFree() helper functions for
 MADV_FREE

On Wed, 4 Mar 2020, David Hildenbrand wrote:

> In general, I don't think this patch really improves the situation ...
> it's only a handful of places where this change slightly makes the code
> easier to understand. And there, only slightly ... I'd prefer better
> comments instead (e.g., in PageAnon()), documenting what it means for a
> anon page to either have PageSwapBacked() set or not.
> 

Agreed, I think any changes to clarify what PageSwapBacked means when it's 
set and when it's clear for PageAnon should be in the form of a comment, 
likely in page-flags.h.  That's currently lacking for lazy free pages.