From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lgeamrelo07.lge.com (lgeamrelo07.lge.com [156.147.51.103]) (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 9864F265621 for ; Sun, 14 Jun 2026 08:20:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=156.147.51.103 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781425220; cv=none; b=GTkhlzs3OhsZtGrKR2OVzygoQqAv1LSIfz9RwTQUxf4gZK3/mDF9XOteTIKV8JA5x/ZEi8IMWD1T6AvzZdwA/mktArf5gNRnb3X3LlzZyMfj0LAypcdrKVdIX5hWL6lb1wP7HwJ5dP5anX8CdJ/1Ep9HkN6RkMblL1xs/FU46ZE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781425220; c=relaxed/simple; bh=gewyEdyEhtdyYxG+SRF/EqpHzJVs6wnsL55nkCPli0c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nVvqDqCv+SattjcL9QQCPSm/G48ByvAHUVXzWogio0nL/Bzh9ji2Z6HRyBhxpJqIg0/XkthjUP0W9BRJEGx36lDohTGsDDsCk1KH8k4FYeSRgDpZ1ORPcQGbuKkzFavaEmTGxJLIXBvDhHWQW60/eRBDb+DNVobJEOsdvIqpyd4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lge.com; spf=pass smtp.mailfrom=lge.com; arc=none smtp.client-ip=156.147.51.103 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lge.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lge.com Received: from unknown (HELO yjaykim-PowerEdge-T330) (10.177.112.156) by 156.147.51.103 with ESMTP; 14 Jun 2026 17:20:09 +0900 X-Original-SENDERIP: 10.177.112.156 X-Original-MAILFROM: youngjun.park@lge.com Date: Sun, 14 Jun 2026 17:20:08 +0900 From: YoungJun Park To: Nhat Pham Cc: akpm@linux-foundation.org, chrisl@kernel.org, kasong@tencent.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, yosry@kernel.org, david@kernel.org, muchun.song@linux.dev, shikemeng@huaweicloud.com, baoquan.he@linux.dev, baohua@kernel.org, chengming.zhou@linux.dev, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, qi.zheng@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, riel@surriel.com, gourry@gourry.net, haowenchao22@gmail.com, kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [RFC PATCH v2 0/7] mm, swap: Virtual Swap Space (Swap Table Edition) Message-ID: References: <20260612193738.2183968-1-nphamcs@gmail.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260612193738.2183968-1-nphamcs@gmail.com> ... > * Integration with swap.tier by Youngjun (see [12]). For now, I'm > leaning towards opting out the vswap device from swap.tier entirely, and > treat it as a special device. Integrating it with swap.tiers will > benefit the cases where you want some cgroups to skip vswap for fast > swap devices (pmem), whereas other should go through zswap first. But > most other use cases, either the overhead of vswap will be acceptable > (or not the bottleneck), or we can just disable CONFIG_VSWAP entirely :) > > Youngjun, may I ask for your thoughts on this? Hi Nhat, Tier 1: VSWAP, Tier 2: ZSWAP ... I don't see any problem applying the desired functionality with the currently proposed mechanism and interface. With this, a user would be assigned the default Virtual -> RAM swap tier, and the overall picture becomes one where swap tiers are composed according to the priority setting. A few more thoughts came to mind. Shakeel also proposed a per-tier max for the swap tier interface. https://lore.kernel.org/linux-mm/aiw2p5ANjsQUCIHA@linux.dev/ However, for vswap, rather than treating it as a case for limiting the amount via such a per-tier max, I think the current interface is the better fit. (But, as Shakeel mentioned, if we only allow the limit to be set to 0 or max, the usage could end up being the same. I'm still thinking this part through.) I have a few other thoughts as well, but I plan to raise those points in the swap tier discussion thread instead. Please take a look at the related thread, and let me know if you have any opinions. :) And I'll share more if other thoughts come to mind Thanks, Youngjun Park