From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 56E7B1EB5FD; Sat, 12 Sep 2026 07:24:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789197878; cv=none; b=ldRlZerscuRymcYXIg/AYMInpl/Tc+Eb2HpUhkNpwdvNz+qkV8E47t77/mdpuZTkEHJz6AOf/b7lrpqUbuOb5n4OJfovCtR4dN06GbZ2Yv85LT/ORRARAtnsQpWHLkRaaEJ7BDRRm3zvGf3RzMAGqIFaDXuFS6sJu04iz6oRa7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789197878; c=relaxed/simple; bh=Vq6CuhOmMOD+AuijHvtaj4qgpqMspuQOm/HUNibe87s=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=D6f0PIXrUq0W49PguhgZmPckLzvTwGJSlU3mszVBe4haZQvmVBzJlNcI4hTz/0/fXcC+I3q53m0m0uRF39DoJ9gKmD4K/8fcGNXHiq7TubznZzcTn8LQoEMmm4SPLR9n82XL5F9gcaawZHkL9s4nq/V87zidgzo2yh/49XK2MwI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=u4T5MVu6; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="u4T5MVu6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B2D351F000FF; Sat, 12 Sep 2026 07:24:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789197877; bh=0cVaMglGGiME75tsb7SvlcJkfEJutw8BxSeMbD4GcdM=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=u4T5MVu64uZuawXIlBM7drVa70yy5BYJ2yh6jb//uLAo+4ZfEmFSzfT4UXOu0bmUw es5sSjwkUQXaXwOvvFFNNDQkkU89KRv/JEsdfiyyh/5Wyxb8NCRP0IkdEQyXedTZgf A4WLQ22J62HhIKJIa3X+2u738nfNxA9PATyYjSfw= Date: Sat, 12 Sep 2026 00:24:36 -0700 From: Andrew Morton To: Suren Baghdasaryan Cc: liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, david@kernel.org, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, xueyuan.chen21@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v4 0/7] read proc/pid/smaps_rollup under per-vma lock Message-Id: <20260912002436.0605a85b912eb8ae406cecf0@linux-foundation.org> In-Reply-To: <20260911194145.1781926-1-surenb@google.com> References: <20260911194145.1781926-1-surenb@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 11 Sep 2026 12:41:38 -0700 Suren Baghdasaryan wrote: > proc/pid/smaps_rollup can be read using the combination of RCU and > VMA read locks, similar to proc/pid/{maps|smaps|numa_maps}. RCU is > required to safely traverse the VMA tree and VMA lock stabilizes the > VMA being processed and the pagetable walk. > Note that we have to keep the logic to drop mmap_lock on contention > because even when using per-VMA locks we might have to fall back to > holding the mmap_lock. Nice. Queued, thanks. The speedups described in [6/7] are significant, although I don't know how representative Paul's tests are. Probably not very. So I don't know how much improvement our users will be seeing from these changes? And I don't know how much usage smaps_rollup gets in the real world? As I've no doubt you know, Sashiko is saying things. About these patches and about the current code. Its pre-existing clear_soft_dirty_pmd() driveby find looks significant. https://sashiko.dev/#/patchset/20260911194145.1781926-1-surenb@google.com