linux-kernel - Re: [PATCH v2 0/1] mm/ksm: recover from memory failure on KSM page by migrating to healthy duplicate

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Message-ID: <c6b60121-61ed-493b-baa5-3d55db68435a@redhat.com>
Date: Thu, 23 Oct 2025 18:16:00 +0200
From: David Hildenbrand <david@...hat.com>
To: Long long Xia <xialonglong2025@....com>, linmiaohe@...wei.com,
 lance.yang@...ux.dev
Cc: markus.elfring@....de, nao.horiguchi@...il.com,
 akpm@...ux-foundation.org, wangkefeng.wang@...wei.com, qiuxu.zhuo@...el.com,
 xu.xin16@....com.cn, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 0/1] mm/ksm: recover from memory failure on KSM page by
 migrating to healthy duplicate

On 21.10.25 16:00, Long long Xia wrote:
> Thanks for the reply.
> 
> I do some simple tests.
> I hope these findings are helpful for the community's review.
> 
> 1.Test VM
> Configuration
> Hardware: x86_64 QEMU VM, 1 vCPU, 256MB RAM per guest
> Kernel: 6.6.89
> 
> Testcase1: Single VM and enable KSM
> 
> - VM Memory Usage:
>     * RSS Total  = 275028 KB (268 MB)
>     * RSS Anon   = 253656 KB (247 MB)
>     * RSS File   = 21372 KB (20 MB)
>     * RSS Shmem  = 0 KB (0 MB)
> 
> a.Traverse the stable tree
> b. pages on the chain
> 2 chains detected
> Chain #1: 51 duplicates, 12,956 pages (~51 MB)
> Chain #2: 15 duplicates, 3,822 pages (~15 MB)
> Average: 8,389 pages per chain
> Sum: 16778 pages (64.6% of ksm_pages_sharing + ksm_pages_shared)
> c. pages on the chain
> Non-chain pages: 9,209 pages
> d.chain_count = 2, not_chain_count = 4200
> e.
> /sys/kernel/mm/ksm/ksm_pages_sharing = 21721
> /sys/kernel/mm/ksm/ksm_pages_shared = 4266
> /sys/kernel/mm/ksm/ksm_pages_unshared = 38098
> 
> 
> Testcase2: 10 VMs and enable KSM
> a.Traverse the stable tree
> b.Pages on the chain
> 8 chains detected
> Chain #1: 458 duplicates, 117,012 pages (~457 MB)
> Chain #2: 150 duplicates, 38,231 pages (~149 MB)
> Chain #3: 10 duplicates, 2,320 pages (~9 MB)
> Chain #4: 8 duplicates, 1,814 pages (~7 MB)
> Chain #5-8: 4, 3, 3, 2 duplicates (920, 720, 600, 260 pages)

Thanks, so I assume the top candidates is mostly zeropages and stuff 
like that.

Makes sense to me then, it would be great to add that as motivation to 
the cover letter!

-- 
Cheers

David / dhildenb