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b=hxtT42Qap/OR/BZVQ+kWHjpYdObAqawVX0mN7pc9AcALNJrZE+K3aWaYr66kRnIxU 37WwL+D03qGWB9DT560Dp7NY1KFxReTS0HqSikgfwznJw7Na5bPCAyfoe64hSlUn7A AZHGEXNfgaIc8hcAJd1r6xKapcDvKvvTNxtievbA2pJDCW/oFY19WJZgHDU/W0FefJ YJ8CZouOi19PQTG15tNlFuKLmmnxQaSJrdBO18qYyk4ranEpCDBiXfPxXi6VC6WpZX nUZC6jj2Ao3gplEPqeXdFmP5JNLqfdo4UJ7/fHdU4kcAE7ivyL29n7X0FYqCy4zEK9 x37mITIQrDj7Q== Message-ID: Date: Thu, 9 Apr 2026 13:59:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: =?UTF-8?B?UmU6IOetlOWkjTogW1BBVENIIHYzIDIvMl0ga3NtOiBPcHRpbWl6ZSBy?= =?UTF-8?Q?map=5Fwalk=5Fksm_by_passing_a_suitable_address_range?= To: xu.xin16@zte.com.cn, shr@devkernel.io, ljs@kernel.org Cc: hughd@google.com, akpm@linux-foundation.org, chengming.zhou@linux.dev, wang.yaxin@zte.com.cn, yang.yang29@zte.com.cn, michel@lespinasse.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260409185610930gKQqJsFs5KoTU4S8MrflI@zte.com.cn> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: nkctwa1gsec7m91caousdc64nbhrkrgc X-Rspamd-Queue-Id: 2DFA21C0008 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1775735995-699087 X-HE-Meta: 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 JmvxwwiB wVyZCh+RQf4Dv/ySSOsLFH9NKUCVaNHQV3gqU4Eu6oucwj4D1XOTZQ+hSFOJ07jLHjbkG7W7AXOlvguOM9D9UL2Bh17XOOXJFjCGnEnmWqWWspaEo3XMGyIzKroDz1kQf0hCVWzNKGYtSUue8lWu8xgx6L3lRkOQiYBfVg9cjt7xGPIHlnQR/7zbQuq+ChkBIrin1vFLqTax0ZHxMA6U1ygnhXQXn8e6/OChgUEs/K0m2WISjSmcVyXvLurMjF91oWCu1143zkpnVE8PDKyItEravKXbmV/h4xfTucyGX0pP2E2lr+97HmdvGbMjZTjh03vrBud+V+fpXE4XM14enpli2eb1uVH2fuAAFuzEDvTHmzpLmXnf4o9qSy7bwQntUviIqlGK4weZXjyU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/9/26 12:56, xu.xin16@zte.com.cn wrote: >> On 4/9/26 11:41, David Hildenbrand (Arm) wrote: >>> >>> As we're using a dedicate kmem cache it might "only" add 8 bytes, not >>> sure. Still an undesired increase given that we need that for each entry >>> in the stable/unstable tree. >>> >> >> Hmm, maybe we could do the following. I think the other members are only >> relevant for the unstable tree. > > Well, I suspect that "SmartScan-Related" members might be also needed and used even when > > it's a stable rmap_item. In should_skip_rmap_item(), if its page is KSM, it can't be skip. Yes, needs some more thought on details. We might have to ignore/skip the fields for stable tree entries that have not a KSM page. > > What if the rmap_item is stable, but its page is not KSM? I guess that would happen if we had a rmap_item at that address, and then changed the page (e.g., COW). ksm_do_scan() would call cmp_and_merge_page() after obtaining such an rmap item from scan_get_next_rmap_item(). In cmp_and_merge_page() we'd call remove_rmap_item_from_tree() and recalculate the checksum. In remove_rmap_item_from_tree() we remove the item from the stable tree. So we'd want to ignore the entries in STABLE_FLAG in scan_get_next_rmap_item() to then reinitialize the fields in cmp_and_merge_page() after remove_rmap_item_from_tree() I guess. -- Cheers, David