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 8D10737204C for ; Tue, 12 May 2026 14:09:07 +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=1778594947; cv=none; b=i0H1xMuUSooLt0naXUSenTHqLVr2F+aiiYhGazRthZeX9vsJ5sIJThhShESyLXAsm9Svy0Q50M58TQYo1z+Qz84eU6u7Dy/IxN2deMYhxYUjI3bU3flSmhgmLyXv7LdvXZh8dx/kFkQzNYrTDywK+JXSdeD6pBuA36Dq+cxkgsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778594947; c=relaxed/simple; bh=M6X22T2O9RgYZBI/BkEj/v2QLQi0oYq5BYAoCkvxfuQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=MKX/I4ZkV+bSR4mrNuQxL/8EMP+i/JOBuRDLjQyyycFKsqStfSVv73zxYZyT+mNzWtmWU1nY4NrLeOk8Fwmb+n5mmimGKkEErgb0SlGVovf18IUAfum9oYh7OeO3uS/NwhDsyHLfZ4iEs3aHygKhkxdxPE5u6FsCbLbu0RsP/v8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VkZe/WFS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VkZe/WFS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 24F79C2BCB0; Tue, 12 May 2026 14:09:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778594947; bh=M6X22T2O9RgYZBI/BkEj/v2QLQi0oYq5BYAoCkvxfuQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VkZe/WFSuj2qphIdEos+JKuocohvTsGiCAtNapnNm/aM0jFSc777+gDrDZV553DQ2 fIJjRYQVKFnKJ1Q5TEhtK6aysXdSRNU3OxXhGA9omEu+KbBRKX6fYeg7q3hgnEnGBq gR4Dcf+YG/86EYn6GCQ6lxpFKjbMfxCo5fmq7QH4vn3x1TiD/7OiIIRNChkQCuAlNq UEIhpfMVmUNy7yHfY8B8TO7bg8XA9hOh7gudXJCGxWgQT5DqpgL2GW/MPqB70+nRL5 miwmpdKHWHQJGVQ4ZMw0gTSdm9vX+iWdID4XuYTpDC6I0ybKFcvKZ+xY/xdiX3JioH 0ibk0HktNvOYQ== From: SeongJae Park To: Kefeng Wang Cc: SeongJae Park , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, sunnanyong@huawei.com Subject: Re: [PATCH] mm/damon/vaddr: attempt per-vma lock during page table walk Date: Tue, 12 May 2026 07:08:52 -0700 Message-ID: <20260512140854.111278-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <618380f2-ea7b-4855-9dc5-d655dc30d5a7@huawei.com> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Tue, 12 May 2026 21:59:26 +0800 Kefeng Wang wrote: > > > 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]， For other readers who may want to read the Sashiko review and might want to commeent, it is also available [1] at lore. > 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? Looks good to me, thank you! Could you send v2 with this change? > > Thanks. > > [1] > https://sashiko.dev/#/patchset/20260511132546.1973270-1-wangkefeng.wang@huawei.com?part=1 [1] https://lore.kernel.org/20260512052628.83798C2BCC7@smtp.kernel.org Thanks, SJ [...]