linux-kernel - Re: [Regerssion] [KSM] KSM CPU overhead in 6.16+ kernel compared to <=6.15 versions ("folio_walk

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Message-ID: <26a8f0aa-8d67-47ba-841c-2daf7010a2aa@redhat.com>
Date: Mon, 13 Oct 2025 21:58:59 +0200
From: David Hildenbrand <david@...hat.com>
To: craftfever@...ena.io
Cc: akpm@...ux-foundation.org, chengming.zhou@...ux.dev,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 lorenzo.stoakes@...cle.com, regressions@...ts.linux.dev, xu.xin16@....com.cn
Subject: Re: [Regerssion] [KSM] KSM CPU overhead in 6.16+ kernel compared to
 <=6.15 versions ("folio_walk_start" kernel object overhead)

On 13.10.25 21:54, craftfever wrote:
> 
> Unfortunately, yes I can reproduce it. And I thought that lockups does
> not happen anymore, but I was wrong, I booted today with 6.17.2 updated
> and KSM enabled and whole situation is back. But, it only happens, when
> scanning pages corresponding to a process with huge VM size, like
> Chromium with 1TB of virtual memory. The rest is alright. It's look
> like, that the folio_walk_start called with much higher frequency, than
> in 6.12-6.15 versions. in that version page scanning of huge VM size
> processes is pretty fast and flawless) Right now, when Chromium is
> running, I expecting constant 42% folio_walk_start and 15%
> ksm_scan_thread on 6.17.2 kernel (contrary to 1% folio_walk_start and
> even less ksm_scan_thread in 6.12-6.15). I must admin that whole system
> is not freezing, just Chromium with high CPU usage from ksmd and kernel.

What about 6.16?

-- 
Cheers

David / dhildenb