From: David Hildenbrand <david@redhat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
Pedro Falcato <pfalcato@suse.de>, Xu Xin <xu.xin16@zte.com.cn>,
Chengming Zhou <chengming.zhou@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 0/4] mm: ksm: prevent KSM from entirely breaking VMA merging
Date: Mon, 19 May 2025 13:53:43 +0200 [thread overview]
Message-ID: <135556a3-9b72-4ec0-acc3-21ee0d15ebe3@redhat.com> (raw)
In-Reply-To: <cover.1747431920.git.lorenzo.stoakes@oracle.com>
On 19.05.25 10:51, Lorenzo Stoakes wrote:
> When KSM-by-default is established using prctl(PR_SET_MEMORY_MERGE), this
> defaults all newly mapped VMAs to having VM_MERGEABLE set, and thus makes
> them available to KSM for samepage merging. It also sets VM_MERGEABLE in
> all existing VMAs.
>
> However this causes an issue upon mapping of new VMAs - the initial flags
> will never have VM_MERGEABLE set when attempting a merge with adjacent VMAs
> (this is set later in the mmap() logic), and adjacent VMAs will ALWAYS have
> VM_MERGEABLE set.
Just to clarify, you mean that VM_MERGEABLE is set later, during
__mmap_new_vma()->ksm_add_vma()->__ksm_add_vma(), and we are already
past vma_merge_new_range(), correct?
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2025-05-19 11:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-19 8:51 Lorenzo Stoakes
2025-05-19 8:51 ` [PATCH 1/4] mm: ksm: have KSM VMA checks not require a VMA pointer Lorenzo Stoakes
2025-05-19 17:40 ` David Hildenbrand
2025-05-20 3:14 ` Chengming Zhou
2025-05-19 8:51 ` [PATCH 2/4] mm: ksm: refer to special VMAs via VM_SPECIAL in ksm_compatible() Lorenzo Stoakes
2025-05-19 17:41 ` David Hildenbrand
2025-05-20 3:15 ` Chengming Zhou
2025-05-19 8:51 ` [PATCH 3/4] mm: prevent KSM from completely breaking VMA merging Lorenzo Stoakes
2025-05-19 13:08 ` Chengming Zhou
2025-05-19 13:13 ` Lorenzo Stoakes
2025-05-19 13:19 ` kernel test robot
2025-05-19 13:36 ` Lorenzo Stoakes
2025-05-19 18:00 ` David Hildenbrand
2025-05-19 18:04 ` David Hildenbrand
2025-05-19 19:02 ` Lorenzo Stoakes
2025-05-19 19:11 ` David Hildenbrand
2025-05-19 19:26 ` Lorenzo Stoakes
2025-05-19 19:29 ` David Hildenbrand
2025-05-19 18:52 ` Lorenzo Stoakes
2025-05-19 18:59 ` David Hildenbrand
2025-05-19 19:14 ` Lorenzo Stoakes
2025-05-19 19:18 ` Lorenzo Stoakes
2025-05-19 19:28 ` David Hildenbrand
2025-05-19 21:57 ` Andrew Morton
2025-05-20 5:25 ` Lorenzo Stoakes
2025-05-20 3:55 ` Chengming Zhou
2025-05-20 5:24 ` Lorenzo Stoakes
2025-05-19 8:51 ` [PATCH 4/4] tools/testing/selftests: add VMA merge tests for KSM merge Lorenzo Stoakes
2025-05-21 8:07 ` Chengming Zhou
2025-05-21 8:10 ` Lorenzo Stoakes
2025-05-19 11:53 ` David Hildenbrand [this message]
2025-05-19 11:56 ` [PATCH 0/4] mm: ksm: prevent KSM from entirely breaking VMA merging Lorenzo Stoakes
2025-05-21 18:20 Lorenzo Stoakes
2025-05-21 18:23 ` Lorenzo Stoakes
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