linux-kernel - Re: [PATCH v7 05/24] mm: devmap: refactor 1-based refcounting for ZONE

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Date:   Thu, 21 Nov 2019 14:22:24 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Jonathan Corbet <corbet@....net>,
        Jérôme Glisse <jglisse@...hat.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Paul Mackerras <paulus@...ba.org>,
        Shuah Khan <shuah@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, <bpf@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>, KVM list <kvm@...r.kernel.org>,
        <linux-block@...r.kernel.org>,
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        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Netdev <netdev@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 05/24] mm: devmap: refactor 1-based refcounting for
 ZONE_DEVICE pages

On 11/21/19 8:59 AM, Dan Williams wrote:
> On Thu, Nov 21, 2019 at 12:57 AM John Hubbard <jhubbard@...dia.com> wrote:
>>
>> On 11/21/19 12:05 AM, Christoph Hellwig wrote:
>>> So while this looks correct and I still really don't see the major
>>> benefit of the new code organization, especially as it bloats all
>>> put_page callers.
>>>
>>> I'd love to see code size change stats for an allyesconfig on this
>>> commit.
>>>
>>
>> Right, I'm running that now, will post the results. (btw, if there is
>> a script and/or standard format I should use, I'm all ears. I'll dig
>> through lwn...)
>>
> 
> Just run:
> 
>      size vmlinux
> 

Beautiful. I thought it would involve a lot more. Here's results:

linux.git (Linux 5.4-rc8+):
==============================================
   text	   data	    bss	    dec	    hex	filename
227578032	213267935	76877984	517723951	1edbd72f	vmlinux


With patches 4 and 5 applied to linux.git:
==========================================
   text	   data	    bss	    dec	    hex	filename
229698560	213288379	76853408	519840347	1efc225b	vmlinux


Analysis:
=========

This increased the size of text by 0.93%. Which is a measurable bloat, so
the inlining really is undesirable here, yes. I'll do it differently.

thanks,
-- 
John Hubbard
NVIDIA