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b=fK7PnRy1mINc5gLPRbZ/6poyoyt3t0M5bTbyMiyuB+bCopIZKet3C9E0v4PFNnI62 5k+oajs2ANDCtmp8bMremIf/p6d8ZT8sdS9ERHa0Eve379SeQIuOT2M/1DidM9MU/X fu5RQE4Lk+uEm1Z6yIBiCSXZHefqC16Kb53h0AvJ4CCDPCNolrnHtE63hLaVwARE3t qn1kbie8UesGRg8N1K72yF7fpHszX+ZMuNWahliLPf6/CxseOWPKrbV7Cl0s1Qlg2b RNsZWj9wqgLcRcdKgEPI6i5U6pMhz+0bX6xueOpDEWd1VA/0YRdMDVk0rsUJyGrfxg 7QgBmSYhw7E8w== Message-ID: Date: Thu, 18 Jun 2026 10:30:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/lruvec: trace LRU add drains and drain-all requests Content-Language: en-US To: "David Hildenbrand (Arm)" , Shakeel Butt Cc: JP Kobryn , linux-mm@kvack.org, willy@infradead.org, usama.arif@linux.dev, akpm@linux-foundation.org, mhocko@suse.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, kasong@tencent.com, qi.zheng@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, youngjun.park@lge.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org References: <20260610195220.12403-1-jp.kobryn@linux.dev> <06122cae-e28b-4ded-a9dd-d380d31c5230@kernel.org> <1136baf3-3967-4202-9eaa-5fd667c235cf@kernel.org> <3149bc84-dd3a-43ba-826e-6364965fdafd@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D59C5180010 X-Stat-Signature: n67jkiebsqcffq6z38bb589agn63csqu X-HE-Tag: 1781771435-118557 X-HE-Meta: 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 DDXSTipz TQSnPd7BYA46w5NWsaVvQGnzc4JJxEEgqEvEkThGs53C4Enx4rB1E/wkBVG4pRoSS2JnNFULkoJvBnNBdNvKuK4kEO7tRrNAm1a/tlEIVE8ge4z/3nqQB0DMB9f0XvXG6m5WrRi9yrOFfJtIHBPHdpNq8ItJN/Kp7khlrbbY47zSponCssg1x4LhZRz551KhwV9ajRvLLLnImvF5A462ZTs0WzOmnH+xqUqM/SsM6I90rCyFL0jmTKvSAhQwAsAlW1w8K Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/18/26 10:21, David Hildenbrand (Arm) wrote: > On 6/17/26 20:18, Vlastimil Babka (SUSE) wrote: >> On 6/17/26 17:03, Shakeel Butt wrote: >>> On Wed, Jun 17, 2026 at 01:11:16PM +0200, David Hildenbrand (Arm) wrote: >>>> >>>> Given that trace events can quickly become stable ABI [1], are we really sure we >>>> want to add this? >>> >>> Yes, I think so as this is useful to get insights into lru cache draining. >>> Trace events being stable or not is secondary IMHO. If in future we rearchitect >>> the lru page handling where there is no cache draining anymore, we can make >>> these a noops. >> >> Yeah and I don't recall ever that a change to a mm tracepoint would ever >> break someone who'd complain and we'd have to revert it. > Really? :) > > Read the context of the link I posted once more. Ah, I see. I've only read the single mail from Steven that referred to the old powertop breakage and didn't notice the context. But I don't think these worries should stop us from adding easily usable tracepoints.