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[160.39.33.242]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8ddb915b738sm1204569985a.32.2026.04.14.14.11.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Apr 2026 14:11:11 -0700 (PDT) Message-ID: Date: Tue, 14 Apr 2026 17:11:10 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] Towards Unified and Extensible Memory Reclaim (reclaim_ext) To: Gregory Price Cc: Matthew Wilcox , Axel Rasmussen , "Lorenzo Stoakes (Oracle)" , Michal Hocko , Andrew Morton , Shakeel Butt , lsf-pc@lists.linux-foundation.org, Johannes Weiner , David Hildenbrand , Qi Zheng , Chen Ridong , Emil Tsalapatis , Alexei Starovoitov , Yuanchu Xie , Wei Xu , Kairui Song , Nhat Pham , Barry Song <21cnbao@gmail.com>, David Stevens , Vernon Yang , David Rientjes , Kalesh Singh , wangzicheng , "T . J . Mercier" , Baolin Wang , Suren Baghdasaryan , Meta kernel team , bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260325210637.3704220-1-shakeel.butt@linux.dev> <20260325190547.abb7309fb63473b57b7a90a0@linux-foundation.org> <6f40c513-af3e-45b6-9000-c61494a23bd3@columbia.edu> Content-Language: en-US From: Tal Zussman In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: C8_wZ-wWAPzE8xbPb-B-t7YDn7TFMUGz X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE0MDE5NyBTYWx0ZWRfX8++vzOFWCoKW ExUMH4heVi39d6tppk09LK5UFIZaqh31rGR78U4+ISNseAiT95LA35BnAIVr8lOdeTX3C96+FyZ D8v1xpIF1XYX4GFpNuAQheIW6/57pCmvXghxeHkDpAbhpdIqhO4n29T5TLgQsBPvgeIpKydgl7b HSSrmWSdtYTpNqd2V82nf3NZUXC/cju6clIIY+gMafHmvcSLPvhVWWS1FsLu7mXAD7ej0h8Y5n5 IX75jlxK2maMKYoosf/1SEUV4ta/YMd97GGr5CL2nYrC7dPxdSssTWR2lqT0evdHjyaMUQroALP PzpDlfb28uOsnUdgXTJ4cuYkIoGzC3tW+cyYrybADQF4cVdrz0LQQ/w67g4hJ2PcBcW8BDz91oz 5WZID21aBkKFbzl3E9D8/snHoyttWjqTcMqGny01dsC8++JPUNCHSjCb7H8RFWByckI7F027X6b /5ARZlC6Jp26KvjcVUA== X-Proofpoint-ORIG-GUID: C8_wZ-wWAPzE8xbPb-B-t7YDn7TFMUGz X-Authority-Analysis: v=2.4 cv=PoWjqQM3 c=1 sm=1 tr=0 ts=69dead71 cx=c_pps a=zwWbXilFUbXn88m9aJbCnw==:117 a=GaPK54s0Se3oFqK5NkZy0g==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=x7bEGLp0ZPQA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=BpGzv1V74M3SfeTrGa8v:22 a=mJhthyEqkmu8OjK3UDMA:9 a=QEXdDO2ut3YA:10 a=t-zOcvtzNAFHAFCEYl37:22 X-Proofpoint-Virus-Version: vendor=nai engine=6800 definitions=11759 signatures=596818 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=10 clxscore=1015 malwarescore=0 spamscore=0 impostorscore=10 bulkscore=10 suspectscore=0 phishscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604140197 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: B936F80011 X-Stat-Signature: cat6hine6rraytgou7wuk598wx18msu4 X-HE-Tag: 1776201074-555875 X-HE-Meta: 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 SXgRTxUS YT8EhLG2Qno5tvJOYyjyCk9/AtAURryUH/czUcyCi/7J7i8Y3to2F+qN3aJ4nPAm9+azFLjb958baENZiJBjsJw+HtrkJ1+rBs5QiFEd0cbIzqfA9uAeWN2guq+zyZR6W4ikBGjwAmV8NXpD10dhXA3sHKuZVb/kHLJBnWtKcj581QYhksGphBZV5PbAukc55n3oduGNmMMR/h5xRNSP9/J6BRcn4s2/++ndRd5RpJaacxbMlQnIcyA+2O4/tjQiP+sCCm2iPDItrQ+DRVvOK8cC96TN/6gRQC+7rrl2Euw+5oW4bc1MCFu7Y3p9xz1Y9UZfVn2V4qfcLiNhfS4Jc6biUDMan3uhHrEsQOoVqX8tw28dpNiCO9CIEJ4ncsP3aHxPI960MVzcn6yk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/27/26 3:43 PM, Gregory Price wrote: > On Fri, Mar 27, 2026 at 03:12:16PM -0400, Tal Zussman wrote: >> >> It's been well-known in the academic realm for a while that there isn't >> really a "one-size-fits-all" policy that works *best* for all workloads. >> Yes, you can make a general policy that works *well*, but if you really care >> about a workload's performance and want to squeeze out the last 10-20% (or >> more) of performance, you need to be able to (1) experiment and (2) take >> advantage of application-level insights. Being able to extend reclaim (in >> our case with eBPF) enables that. >> > > This just makes me think going all the way to reclaim_ext and re-writing > MGLRU as an eBPF extension in an effort to simplify the code/maintenance > and keep what works working is the least-worst option. That may very well be true, at least on the policy side. In fact, we implemented an MGLRU policy in eBPF. The infrastructure side is a different story, as Shakeel has pointed out. > But this is a naive take, i'm sure making that interface stable would be > even worse than just maintaining both LRU/MGLRU. Putting eBPF aside for a second, I'm of the opinion that separating reclaim policy from infrastructure and creating such an interface would actually be beneficial for maintenance long-term. There's no clean separation between policy and infrastructure right now, making the code less readable and potentially affecting performance. I'm in the process of collecting some instances of such overlap and assessing what their impact is. Now, once you have such an interface... eBPF falls into place pretty nicely... Thanks, Tal