From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout03.his.huawei.com (canpmsgout03.his.huawei.com [113.46.200.218]) (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 021073A05EB for ; Tue, 12 May 2026 13:59:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778594380; cv=none; b=udCjSNzcUk9aifSriRYysV7cpQEH4ZDF293dLr0N60ISkgGy7oop8T+f1fRF65po8qr+D+a6biyNQLFf1Hutto5HaXPvFizetsQMet+tX4JwGzMQVOJ7puLlvuto6e6CgAEeXyPcPoPwpwzLlE6baLniG9E0B+rfi2Y4jXpc/rY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778594380; c=relaxed/simple; bh=6rwi5Oyq1EeQUFIxFWOFOXFySDtgPAJDCKpAx1QkZkU=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=B/uvmJp5RuR/uz87oMdadOAkH/dkfGbwQpDSwI9xCud2vaN0373rbc3CX8YVtOxRQVseLoRGVie6M72R6OsO7b/J32mbrBnLP51O81T9HLzsCAMyneii3L6iyvHhYfLk+f1tpV5Fk1uVXDCCWQCCQI+ym45MZhktD0vTzXeBFNk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=BZh00c5k; arc=none smtp.client-ip=113.46.200.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="BZh00c5k" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=xjBHpnrtr7TLQ5ApPzHZqIHU3mdRNFOc4hxIvr8BBVw=; b=BZh00c5kQpek7iEJf+pa1l7R5vnaN0BHDZahQdoGUW2q8mJtx42R7I4CAjy3+YKGirlEmmH4I tem5nRl57aI+6No+0FGmkRDT2Q7zyI58mNmxRswVrE7OvmwTpw3DweyoNcdDsX0xTZX6f876k1N sEeCR90d1G6g1/V8mZfCZK0= Received: from mail.maildlp.com (unknown [172.19.163.0]) by canpmsgout03.his.huawei.com (SkyGuard) with ESMTPS id 4gFJ1n0nHnzpStD; Tue, 12 May 2026 21:52:29 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 2D04D40561; Tue, 12 May 2026 21:59:29 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 12 May 2026 21:59:28 +0800 Message-ID: <618380f2-ea7b-4855-9dc5-d655dc30d5a7@huawei.com> Date: Tue, 12 May 2026 21:59:26 +0800 Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/damon/vaddr: attempt per-vma lock during page table walk To: SeongJae Park CC: Andrew Morton , , , References: <20260512013116.80435-1-sj@kernel.org> Content-Language: en-US From: Kefeng Wang In-Reply-To: <20260512013116.80435-1-sj@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To dggpemf100008.china.huawei.com (7.185.36.138) On 5/12/2026 9:31 AM, SeongJae Park wrote: > On Mon, 11 May 2026 21:25:46 +0800 Kefeng Wang wrote: > >> Currently, DAMON virtual address operations use mmap_read_lock >> during page table walks, which can cause unnecessary contention >> under high concurrency. >> >> Introduce damon_va_walk_page_range() to first attempt acquiring a >> per-vma lock. If the VMA is found and the range is fully contained >> within it, the page table walk proceeds with the per-vma lock >> instead of mmap_read_lock. >> >> This optimization is particularly effective for damon_va_young() >> and damon_va_mkold(), which are frequently called and typically >> operate within a single VMA. > > Makes sense. Do you have some measurements? In fact, I do not have performance-related tests. > >> >> Signed-off-by: Kefeng Wang > > Looks good to me. Nonetheless, because I'm not familiar with per-vma locking, > I'd like to wait for Sashiko review. > Sashiko review reports a issue about handling VMAs with the VM_PFNMAP flag inconsistently[1]，We indeed do not need to handle the vma of VM_PFNMAP for damon, so a quick fix is as follows, diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index eed2ae132a58..d27147603564 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -251,8 +251,11 @@ static void damon_va_walk_page_range(struct mm_struct *mm, unsigned long start, goto lock_mmap; } - ops->walk_lock = PGWALK_VMA_RDLOCK_VERIFY; - walk_page_range_vma(vma, start, end, ops, private); + if (!(vma->vm_flags & VM_PFNMAP)) { + ops->walk_lock = PGWALK_VMA_RDLOCK_VERIFY; + walk_page_range_vma(vma, start, end, ops, private); + } + vma_end_read(vma); return; Any more comments? Thanks. [1] https://sashiko.dev/#/patchset/20260511132546.1973270-1-wangkefeng.wang@huawei.com?part=1 > > Thanks, > SJ > > [...] >