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imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of youngjun.park@lge.com designates 156.147.23.51 as permitted sender) smtp.mailfrom=youngjun.park@lge.com; dmarc=pass (policy=none) header.from=lge.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783959768; b=7eZ24M5YXb446H2PSI0WGxs7REy2PX7KaKKzrVbfh7zDBFWxH1qVNBruawVnaTyDnQQmoJ Vvtlwun1IGFDBf728lbnXiLp1qZevZf9//EbnsU6Wv3XJBnaMDuw8Jz+0D0gsCafBEzZTI ilchnRCe0LBf9rDrRY5bELEFAZHC80U= Received: from unknown (HELO lgemrelse7q.lge.com) (156.147.1.151) by 156.147.23.51 with ESMTP; 14 Jul 2026 01:22:42 +0900 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: youngjun.park@lge.com Received: from unknown (HELO yjaykim-PowerEdge-T330) (10.177.112.156) by 156.147.1.151 with ESMTP; 14 Jul 2026 01:22:42 +0900 X-Original-SENDERIP: 10.177.112.156 X-Original-MAILFROM: youngjun.park@lge.com Date: Tue, 14 Jul 2026 01:22:42 +0900 From: Youngjun Park To: Yosry Ahmed Cc: akpm@linux-foundation.org, chrisl@kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kasong@tencent.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, shikemeng@huaweicloud.com, baoquan.he@linux.dev, baohua@kernel.org, joshua.hahnjy@gmail.com, gunho.lee@lge.com, taejoon.song@lge.com, hyungjun.cho@lge.com, baver.bae@lge.com, her0gyugyu@gmail.com Subject: Re: [PATCH v10 0/6] mm/swap, memcg: Introduce swap tiers for cgroup based swap control Message-ID: References: <20260713025644.170839-1-youngjun.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A4ABB10000F X-Stat-Signature: qp816x17qohx8i8813sntshopptjcsi4 X-HE-Tag: 1783959766-735674 X-HE-Meta: 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 2+D9a6aZ kMsKy3y7VSHJfzmiiQBqe1nD7UKToDbKn+W4d9KUuyGT5qNBBrz22DVS5TS4XVbB0UnAxMqf+6GHJefZAkLAYeJ9asTHZfaKPoG9RXFP92k/YWwbksp8gq+vvipjSrm/t4r62quJmCAAZxPOCVvyuMvJdmV0zXe2+fv12hysPqEngC23i9E/E6r6VGznnTHwM79wyPqVCp/oAjycfnI2XOYemzLL47wrE4n+BYf7FJyP+DIbLupSR85TjJhb+k7gGR6UTq2BdMo3AniZ3s0EJWSDuNE61a+6eten+v9+3DtM5ps+34d2DpQi+zHZX82I41p94oVUac90xCRCWC5aNMglr4w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jul 13, 2026 at 09:01:20AM -0700, Yosry Ahmed wrote: > On Mon, Jul 13, 2026 at 8:57 AM Youngjun Park wrote: > > > > On Mon, Jul 13, 2026 at 08:50:36AM -0700, Yosry Ahmed wrote: > > > On Sun, Jul 12, 2026 at 7:57 PM Youngjun Park wrote: > > > > > > > > This is the v10 series of the swap tier patchset. > > > > > > > > v10 folds in the Sashiko review fixes for the selftests added in v9 and > > > > rebases onto the current mm-new. There are no functional changes to the > > > > core swap or memcg code since v9; see the changelog for details. > > > > > > > > For context, the bulk of the series is unchanged since v8, with great thanks > > > > to Shakeel Butt and Yosry for the reviews and discussions [1] that shaped it. > > > > The main change in v8 was the interface change to use memory.swap.tiers.max > > > > with '0' (disable) and 'max' (enable) values. This mechanism was suggested > > > > by Shakeel and Yosry. > > > > > > > > This change allows for future extensions to control swap between tiers and > > > > aligns better with existing memcg interfaces. It is confined to patch #3's > > > > user-facing interface; internally, patch #3 still uses the existing mask > > > > processing method, which is implementation-efficient. > > > > > > > > We also discussed tier extensions. Thanks to Yosry, Nhat and Shakeel for their > > > > valuable feedback. > > > > > > > > Here is a brief summary of our tentative conclusions. Please correct me > > > > if anything is misrepresented (details in references): > > > > > > > > * Zswap tiering [2]: > > > > Zswap can itself be a tier (typically the fastest one). But, until vswap lands, > > > > zswap cannot be the only allowed tier, > > > > since it still needs a physical device for allocation; > > > > that restriction can be lifted once vswap is supported. > > > > > > Does this series support zswap being a tier? I cannot find any mention > > > of zswap in the patches. > > > > Hello Yosry! > > > > This series does not cover zswap as a tier yet. > > > > My plan is to land the swap tier infrastructure together with the > > first use case (cgroup-based swap control) first, and then follow > > up with zswap tier support in a subsequent series, continuing the > > discussions we've had above. > > (I mentioned on cover letter, right above the overview section) > > > > Does that approach sound reasonable to you? > > How does swap tiering work with zswap in the current series? I assume > zswap is just enabled for all devices in all tiers? Yes, that's correct. > I wonder if introducing zswap as a tier after the fact changes user-visible > behavior. I guess if zswap will be introduced with a default "max" > value it will more-or-less be the same behavior, Right, that's the plan. > but I would check all > user-visible behaviors related to zswap (e.g. interaction with other > zswap interfaces) to make sure nothing breaks or changes in a > meaningful way when zswap is introduced as a tier later. Fair point. Let me review this more and get back to you! Thanks, Youngjun