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Wed, 19 Nov 2025 05:09:49 -0800 (PST) Received: by grain.localdomain (Postfix, from userid 1000) id 3A2A35A0033; Wed, 19 Nov 2025 16:09:49 +0300 (MSK) Date: Wed, 19 Nov 2025 16:09:49 +0300 From: Cyrill Gorcunov To: Lorenzo Stoakes Cc: Andrei Vagin , Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org, criu@lists.linux.dev Subject: Re: [PATCH 0/2] make VM_SOFTDIRTY a sticky VMA flag Message-ID: References: <1c20ec44-0775-47e0-aabb-e1cf1f38ce94@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 81606140006 X-Stat-Signature: snmbf4tpottycn1wz5zfs7gep1zcdmsb X-Rspam-User: X-HE-Tag: 1763557792-190067 X-HE-Meta: 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 o2jGjFTH 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Nov 17, 2025 at 07:57:30PM +0000, Lorenzo Stoakes wrote: ... > > I recall correctly that initially, merging vma-s with different > > VM_SORTDIRTY bit values was not allowed. It was a bit surprising that > > this behavior was changed by Cyrill in 34228d473efe. Cyrill was an > > active CRIU contributor at the time, so we can't even blame anyone for > > breaking CRIU :). > > Well I think Cyrill is in the right here :) the problem described there - > that of hitting the max_map_count simply due to failed VM_SOFTDIRTY merges > - is very serious and clearly highlights the issue that arises from not > merging these - that is VMA fragmentation. Hi guys! Happen to miss this thread due to high message traffic, thanks for CC'ing me ;) Yeah, disability to merge VMAs due to softdirty bit has been a serious issue, so better criu to dump more (redundant) memory than apps got broken. As to this patch series, I think it is good, thanks a huge Lorenzo! Acked-by: Cyrill Gorcunov