linux-kernel - Re: [PATCH RFC 4/4] mm/page_alloc: place pages to tail in __free_pages

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Date:   Mon, 28 Sep 2020 14:53:51 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-hyperv@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-acpi@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Mike Rapoport <rppt@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>
Subject: Re: [PATCH RFC 4/4] mm/page_alloc: place pages to tail in
 __free_pages_core()

On Mon, Sep 28, 2020 at 10:36:00AM +0200, David Hildenbrand wrote:
> Hi Oscar!

Hi David :-)

> 
> Old code:
> 
> set_page_refcounted(): sets the refcount to 1.
> __free_pages()
>   -> put_page_testzero(): sets it to 0
>   -> free_the_page()->__free_pages_ok()
> 
> New code:
> 
> set_page_refcounted(): sets the refcount to 1.
> page_ref_dec(page): sets it to 0
> __free_pages_ok():

bleh, I misread the patch, somehow I managed to not see that you replaced
__free_pages with __free_pages_ok.

To be honest, now that we do not need the page's refcount to be 1 for the
put_page_testzero to trigger (and since you are decrementing it anyways),
I think it would be much clear for those two to be gone.

But not strong, so:

Reviewed-by: Oscar Salvador <osalvador@...e.de>

-- 
Oscar Salvador
SUSE L3