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Wed, 16 Sep 2026 13:04:38 -0700 (PDT) Date: Wed, 16 Sep 2026 16:04:34 -0400 From: Johannes Weiner To: Youngjun Park Cc: akpm@linux-foundation.org, chrisl@kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kasong@tencent.com, 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, yosry@kernel.org, joshua.hahnjy@gmail.com, taejoon.song@lge.com, her0gyugyu@gmail.com, lianux.mm@gmail.com Subject: Re: [RFC PATCH v11 0/4] mm/swap: priority-based swap tiers with per-cgroup selection Message-ID: <20260916200434.GA5784@cmpxchg.org> References: <20260916183437.2946306-1-youngjun.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260916183437.2946306-1-youngjun.park@lge.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0ABCB8000E X-Stat-Signature: uadccs97gntzxwhrcehuia6ttdtrrabo X-Rspam-User: X-HE-Tag: 1789589084-652862 X-HE-Meta: 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 rmbE+Lmi 8vCGf5uZhvGZ0Al+aW29mrSnB4gCBhLRntz3CHt3IBDXHg/7PMGPLrDxr4Pk9zWjH3U7noLt2TBJC0xuf3NCMlYgtOEEWoFuUajWFqyFv8qWqsri7/1UmUliZ+ZYJCXgIzXSQfYrb9CtTVLSzWzZHfFXUcqQ0icMTf4BTXLNZoLc27g5JezcUxMPuj7O3DB0ZyeNpaK1D0X5qowVI1cVqH4pmMJxG9uzRGzw+W4yHkDAm1z17IQyWjc2J+y47vS1o1GZCAPknVUrjBgIhTk64kltxin32r7nkcPAIil/a9HwcX4sPsJFmSyE7b+m9CM2hZ/IMJbIpGybGCTEZzDvtmiqSI7FjW8rZzrBjcawNNB8cg9Ev1f+WdaaRPi9+lwRcfa6kiOf8Xk/2Jw5wb1X4PeYHtg8lHiSq3JrFV+4GrAmDbW522y/QewBk3xzKY88jFMEz07OVE8xF9CCVeBFdlHU4wZ8lwbUPON0S Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 17, 2026 at 03:34:33AM +0900, Youngjun Park wrote: > Per-cgroup swap in debugfs > ========================== > > Patches 3 and 4 let a memory cgroup choose its tiers through debugfs. > > # swapon -p 100 /dev/nvme0n1p2 > # swapon -p 50 /dev/sdb2 > # cat /sys/kernel/debug/swap/tiers > Idx Prio > 0 100 > 1 50 > # echo "/batch 0x2" > /sys/kernel/debug/swap/memcg_tiers > > Bit i of the mask is tier i, so /batch swaps only to sdb2. A tier keeps > its index for its lifetime, so the mask keeps selecting the same tier > across swapon and swapoff. Can the cgroup be given a priority limit? That would have pretty obvious inheritance semantics: root `- batch (memory.swap.prio.max = 20) `- task (memory.swap.prio.max = max) `- logs (memory.swap.prio.max = 10) `- interactive (memory.swap.prio.max = max) `- task (memory.swap.prio.max)