From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8CA523C1987 for ; Thu, 9 Apr 2026 11:59:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775735994; cv=none; b=auflVNXUpXtzX73SkXBUmmKDM08qX0F+RFHJRgMZRCUJ4O8mYyyCseSSV63VxMWZqe1CLjRnAXK2uyrL7Qbywg/0OAzZK7vVgVPg/ToRfWO8eEnno+/oeNw83vpxzCuUnSqNJo7evzvsC/nnFcua0VDf6r/crTSUbc0JKw4P8fA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775735994; c=relaxed/simple; bh=fTTkHCuIQCSNmktK8innsRZQWyUUgjZd5seY4VpXbVs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=I2pqwMHxrAjapPODFGInv4tbgeSuZ4u2mOdOlLYC6T85fSD5yVu1ZF3bOzwGwhhO9WwANeHDo2qoVGMH3Z0aJiPotlntgWw51GWyaPG5C+TcODPtYK+JFs74tdxVW4bPzPaaOrx1Sazn8i+2ucDQ4N0o/578x6pB1DhfxTVRSeo= ARC-Authentication-Results:i=1; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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