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Wed, 21 May 2025 10:32:03 -0700 (PDT) Date: Wed, 21 May 2025 13:32:00 -0400 From: Johannes Weiner To: Lorenzo Stoakes Cc: Shakeel Butt , Andrew Morton , "Liam R . Howlett" , David Hildenbrand , Vlastimil Babka , Jann Horn , Arnd Bergmann , Christian Brauner , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, SeongJae Park , Usama Arif Subject: Re: [RFC PATCH 0/5] add process_madvise() flags to modify behaviour Message-ID: <20250521173200.GA1065351@cmpxchg.org> References: <7tzfy4mmbo2utodqr5clk24mcawef5l2gwrgmnp5jmqxmhkpav@jpzaaoys6jro> <5604190c-3309-4cb8-b746-2301615d933c@lucifer.local> <226owobtknee4iirb7sdm3hs26u4nvytdugxgxtz23kcrx6tzg@nryescaj266u> <7a214bee-d184-460f-88d6-2249b9d513ba@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7a214bee-d184-460f-88d6-2249b9d513ba@lucifer.local> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: AD1D7140015 X-Stat-Signature: bctz8di51turmpu545czkwy7agi489fd X-HE-Tag: 1747848725-899657 X-HE-Meta: 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 flOXwx5u D4nOKg93L6yqBmdJKJBHtflVKGnSAj0c3egx24VmzIx/6fu7Ea0xp2F0s5IH194NPmFx7Qjf+cPnsE1COuxvca7OMQuZMidVlj6xATZlx48nPIEoCVRDa53f/t37d5wgx8d5U1AmlLnT1YhG57l5Hzn/Exnco3qByJLlXr56Da7JU/zaw6sMJpQ12ACUYZKpm7LG3b5sUYSN76t08rtOP/Kpfvihkj3qvz/MHYnuu5zD3ZRTx0gL7k5L4YXcB07BltBv6dust4k2csTHriI7eBokOc2/PMiOJIF54YxDdOsEF/8limJ10+tSc0NukkS9MvEPpW0buzfL2dueHB/eebFHF/LLYVf1SSBdwwLjxsFl67/1n5BX+v1b8zYoV0RDQH+sPLwJbFAnp8lbQk/HLcsM4HJBxgZp64Vh57EpVObRGVMg4ymw0Uaxwk7SgYGAuJLdl X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, May 21, 2025 at 05:21:19AM +0100, Lorenzo Stoakes wrote: > So, something Liam mentioned off-list was the beautifully named > 'mmadvise()'. Idea being that we have a system call _explicitly for_ > mm-wide modifications. > > With Barry's series doing a prctl() for something similar, and a whole host > of mm->flags existing for modifying behaviour, it would seem a natural fit. That's an interesting idea. So we'd have THP policies and Barry's FADE_ON_DEATH to start; and it might also be a good fit for the coredump stuff and ksm if we wanted to incorporate them into that (although it would duplicate the existing proc/prctl knobs). The other MMF_s are internal AFAICS. I think my main concern would be making something very generic and versatile without having sufficiently broad/popular usecases for it. But no strong feelings either way. Like I said, I don't have a strong dislike for prctl(), but this idea would obviously be cleaner if we think there is enough of a demand for a new syscall. > I guess let me work that up so we can see how that looks? I think it's worth exploring!