> Emm, after checked the code again, it seems you are right. But this can not explain why i got inaccurate demotion statistics from /proc/vmstat compared to the value i counted in the code myself days ago.
Well... I know what was going on, the second pass will override stat-＞nr_demoted to be *zero* that makes the first try stat-＞nr_demoted got lost.
发件人: Li, Zhijian/李 智坚 <lizhijian@xxxxxxxxxxx>
发送时间: 2025年1月10日星期五 22:20
收件人: Kaiyang Zhao
抄送: linux-mm@xxxxxxxxx; Andrew Morton; linux-kernel@xxxxxxxxxxxxxxx
主题: Re: [PATCH 1/2] mm/vmscan: Accumulate nr_demoted for accurate demotion statistics
＞ It looks like demotion will only be attempted once. On the second pass,
do_demote_pass will be false, demote_folios will be empty and
demote_folio_list() will do nothing. But I guess there is no harm in
making nr_demoted an accumulation for less confusion in the future...
Emm, after checked the code again, it seems you are right. But this can not explain why i got inaccurate demotion statistics from /proc/vmstat compared to the value i counted in the code myself days ago.
thanks for your feedback, i will take a look next week.
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发件人: Kaiyang Zhao <kaiyang2@xxxxxxxxxx>
发送时间: 2025年1月10日星期五 20:50
收件人: Li, Zhijian/李 智坚
抄送: linux-mm@xxxxxxxxx; Andrew Morton; linux-kernel@xxxxxxxxxxxxxxx
主题: Re: [PATCH 1/2] mm/vmscan: Accumulate nr_demoted for accurate demotion statistics
On Fri, Jan 10, 2025 at 08:21:32PM +0800, Li Zhijian wrote:
> In the shrink_folio_list() function, demote_folio_list() can be called
> multiple times, which can lead to inaccurate demotion statistics if the
> number of demoted pages is not accumulated correctly.
It looks like demotion will only be attempted once. On the second pass,
do_demote_pass will be false, demote_folios will be empty and
demote_folio_list() will do nothing. But I guess there is no harm in
making nr_demoted an accumulation for less confusion in the future...
