linux-kernel - Re: [PATCH V5 1/2] mm: compaction: move compaction sysctl to its own file

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Date:   Mon, 27 Mar 2023 12:27:18 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     ye xingchen <yexingchen116@...il.com>, mcgrof@...nel.org
Cc:     akpm@...ux-foundation.org, chi.minghao@....com.cn,
        hch@...radead.org, keescook@...omium.org, linmiaohe@...wei.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, willy@...radead.org, ye.xingchen@....com.cn,
        yzaikin@...gle.com
Subject: Re: [PATCH V5 1/2] mm: compaction: move compaction sysctl to its own
 file

On 3/27/23 04:49, ye xingchen wrote:
>>> >$ ./scripts/bloat-o-meter vmlinux.old vmlinux
>>> >add/remove: 1/0 grow/shrink: 1/2 up/down: 346/-350 (-4)
>>> >Function                                     old     new   delta
>>> >vm_compaction                                  -     320    +320
>>> >kcompactd_init                               167     193     +26
>>> >proc_dointvec_minmax_warn_RT_change          104      10     -94
>>> >vm_table                                    2112    1856    -256
>>> >Total: Before=19287558, After=19287554, chg -0.00%
>>> >
>>> >So I don't think we need to pause this move or others where are have savings.
>>> >
>>> >Minghao, can you fix the commit log, and explain how you are also saving
>>> >4 bytes as per the above bloat-o-meter results?
>>> 
>>> $ ./scripts/bloat-o-meter vmlinux vmlinux.new
>>> add/remove: 1/0 grow/shrink: 1/1 up/down: 350/-256 (94)
>>> Function                                     old     new   delta
>>> vm_compaction                                  -     320    +320
>>> kcompactd_init                               180     210     +30
>>> vm_table                                    2112    1856    -256
>>> Total: Before=21104198, After=21104292, chg +0.00%
>>> 
>>> In my environment, kcompactd_init increases by 30 instead of 26.
>>> And proc_dointvec_minmax_warn_RT_change No expansion.
>>
>>How about a defconfig + compaction enabled? Provide that information
>>and let Vlastimal ACK/NACK the patch.
> I use x86_defconfig and linux-next-20230327 branch
> $ make defconfig;make all -j120
> CONFIG_COMPACTION=y
> 
> add/remove: 1/0 grow/shrink: 1/1 up/down: 350/-256 (94)
> Function                                     old     new   delta
> vm_compaction                                  -     320    +320
> kcompactd_init                               180     210     +30
> vm_table                                    2112    1856    -256
> Total: Before=21119987, After=21120081, chg +0.00%

No savings then, but to me the patch still seems a worthwile cleanup. But if
others think the 94 bytes are an issue, it can wait for the new APIs.