linux-kernel - Re: [PATCH v17 3/9] mm: Add function __putback_isolated

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Message-ID: <20200219143300.GR3466@techsingularity.net>
Date:   Wed, 19 Feb 2020 14:33:00 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     kvm@...r.kernel.org, david@...hat.com, mst@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, yang.zhang.wz@...il.com,
        pagupta@...hat.com, konrad.wilk@...cle.com, nitesh@...hat.com,
        riel@...riel.com, willy@...radead.org, lcapitulino@...hat.com,
        dave.hansen@...el.com, wei.w.wang@...el.com, aarcange@...hat.com,
        pbonzini@...hat.com, dan.j.williams@...el.com, mhocko@...nel.org,
        alexander.h.duyck@...ux.intel.com, vbabka@...e.cz,
        osalvador@...e.de
Subject: Re: [PATCH v17 3/9] mm: Add function __putback_isolated_page

On Tue, Feb 11, 2020 at 02:46:24PM -0800, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
> 
> There are cases where we would benefit from avoiding having to go through
> the allocation and free cycle to return an isolated page.
> 
> Examples for this might include page poisoning in which we isolate a page
> and then put it back in the free list without ever having actually
> allocated it.
> 
> This will enable us to also avoid notifiers for the future free page
> reporting which will need to avoid retriggering page reporting when
> returning pages that have been reported on.
> 
> Acked-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com>

Ok, the prior code that used post_alloc_hook to make the isolated page seem
like a normally allocated page followed by a free seems strange anyway. As
well as being expensive, isolated pages can end up on the per-cpu lists
which is probably not what is desired. I *think* what you've done is ok so

Acked-by: Mel Gorman <mgorman@...hsingularity.net>

-- 
Mel Gorman
SUSE Labs