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b=KWhNYPOan5xPFiCT6IwXfvfrXkuVjX/oWCqOUSeICiPwrZGkX9WJjhqcjJwacxwzL fexJ2d1hVI7uZCaQ/V7pm9RZfn50zIa9bpuRQfLOQHRkFDI4J+IOQA1EK49VtYfvLF t/b5cXp9Rc5ZsEmjlPclmNKjtMk4p0pEm6PQN/DGostcKs+ZoYHFqlGFGGlXTqgxiv btrwUTIPYYqaHUQuGN1m85efSCk0MZL53djPsgeoKt7erFk0fHFvMJrwmAggkh2mF8 rQv31lIwCs4WfpEYwUu4A8u/X7vPTc80Kzq3oK9niFH2dCbtEwkuc9VeoK+ROSw4l3 2eQUGxgZv5aAw== Message-ID: <046e3eef-aae6-4361-821e-06cadf250d49@kernel.org> Date: Mon, 19 Oct 2026 16:21:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2] mm: introduce copy_mc_highpages() and batch copy in folio_mc_copy() To: "Garg, Shivank" , "pfalcato@suse.de" Cc: "tejavojjala@google.com" , "Rao, Bharata Bhasker" , "rppt@kernel.org" , "david.laight.linux@gmail.com" , "ankur.a.arora@oracle.com" , "dave.hansen@linux.intel.com" , "vbabka@kernel.org" , "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "mingo@redhat.com" , "surenb@google.com" , "linux-mm@kvack.org" , "nhuhuan@google.com" , "Salunke, Hrushikesh" , "tglx@kernel.org" , "liam@infradead.org" , "hpa@zytor.com" , "mhocko@suse.com" , "bp@alien8.de" , "ljs@kernel.org" , "rientjes@google.com" , "torvalds@linuxfoundation.org" , "x86@kernel.org" References: <20261019-batpagecopy-v2-1-d75e7d0dfaae@amd.com> <0346e29faa551efb6a4e21a920d344f5f9b918e5.camel@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 0FCD3100006 X-Stat-Signature: rhi1acrb1fdt1mwhg9g6q4jj1e9a5bsg X-Rspam-User: X-HE-Tag: 1792419677-601458 X-HE-Meta: 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 rLanbNij 6rx8rUnDSa8J+uwdmc9BCtuBYAykQW8rROw+3Z04Txxuw+ywcNRcyu6RSv34HMMze9guYOpjhBVZ89l8W2+9RoxPVgzrhzuraV7+SNZD1faeoSQ4yHmAZpQA1Cic+YWtxOkkxs2d/+91vTQ6XZPSwdH+dAexnvIr0cU6Z7KGmDZnnG01KMeJw9WTBEPnZaL8pxstpaqgE2OKXmjSmuzBYJ+62zRJH75mS379rChv88i9lXrPVaxN1/5DhIECPCui00gzWJHYgirKlnL4O9EosYDgZA00RfPe2cb3nKPHSvBlEdRvh9jCByKvKPRleEkWO4S3TOYlIEa+fTv8OfXyiqLQvLX4x/IGXRuDLL7oMN5uNLt7cvb5/rgH82EtoVsZJCcsxpgKRd+WqTeUne/CsBwPeNfsH8gdFDqGpaNCuYQ+tiT8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/19/26 15:10, Garg, Shivank wrote: > On Mon, 2026-10-19 at 14:23 +0200, David Hildenbrand (Arm) wrote: >>> >>> I would suggest that perhaps this should be the fallback for non-preemptible >>> models. But it gets a little weird with PREEMPT_DYNAMIC I think? >> >> Why can't we just use PROCESS_PAGES_NON_PREEMPT_BATCH where we have similar >> handling already? >> >>> > > I did not reuse PROCESS_PAGES_NON_PREEMPT_BATCH because it depends on > whether clear_pages is defined. While COPY_MC_PAGES_NON_PREEMPT_BATCH > depends on copy_mc_to_kernel and other constraints. So, using a single > param for both would make it more messy. If it would stay it would all have to be cleaned up to end up with a single one. > > However as Pedro pointed, most architectures are full preempt/preempt lazy, > and with this commit 7dadeaa6e851 ("sched: Further restrict the > preemption modes"), for PREEMPT_DYNAMIC, preempt=none and preempt=voluntary > are rejected at boot. preempt_model_preemptible() is therefore always > true for this case. > > So, this can be simplfied to drop the COPY_MC_PAGES_NON_PREEMPT_BATCH. Can we simplify the zeroing part as well? -- Cheers, David