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Tue, 29 Apr 2025 16:56:09 -0700 (PDT) Date: Tue, 29 Apr 2025 23:56:08 +0000 From: Wei Yang To: Lorenzo Stoakes Cc: David Hildenbrand , Wei Yang , akpm@linux-foundation.org, riel@surriel.com, vbabka@suse.cz, harry.yoo@oracle.com, jannh@google.com, baohua@kernel.org, linux-mm@kvack.org Subject: Re: [RFC Patch 0/5] Make anon_vma operations testable Message-ID: <20250429235608.yvbcxybkfsmp6ow5@master> Reply-To: Wei Yang References: <20250429090639.784-1-richard.weiyang@gmail.com> <8c268ece-71a7-470a-bf8b-71d3e4920977@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 77E8B8000D X-Stat-Signature: 4wnnbwn7omg16pympo85tt7s6hxn7mpm X-Rspam-User: X-HE-Tag: 1745970971-151666 X-HE-Meta: U2FsdGVkX1/W7GCZW4hqBrAiHtZ+gUvSnJ28kNI76l9JVvfC1n7jNi3IxChVP1wQT41xHK13oQ5w9yK2bYW2JAHw9qhDjMSIrx5R8QVc4apbrUfe48h5LMBVX2FQYK4c2XBcjzNc6/mOFY8F+vAvbV+beEdCTmfxxBJKyzjZ08OYijvMEZ1UpQaa6ZlAUE3eMNFzyhq5Tcf4tu23YbMbAVZxh3E8J6GsMws7KuwSdBiWJn3i6Z3t09GaYuFpsh1tiPBRjAi6h09/MaN4OfptlZzuuToBHqaSWR2AjkreZQPhVnWknqJxSG7/wnQ7SS+yajIwRDXTYnaAv1nS6ev9TbSX+uscs8yf6T9hbE+fMFD6CFfS+EKc/ojOoeqhD4uOGB9zHAQnM48snmoPILo1ajSkhDSuqXLes8CufVOF1K0VQyzazub9MPXPGsSjAh4/4HqZbnZs18PasZMPxAY07tjjjXRrC8L0//9/Gd6JWYICUV2t5dchZ9ZL0wnFOh9TIIjc6zqESWLhJd6qb4435fdYvX7rpGTAx+//zONgq+8R6+unc7AZVgS6GQdjTDn7zynfJKXb9Ip+dvPEAeYyuW58S01ZfYwZZBne1C7xdSgPAz+s4EhLfG+7LSQIJaC3ervfDvrafGp1F2B9Z/N3eC/b76JUHWVMf7iVwVoX+lnsaPvT0vrHtRi2OtARKEvpxpXTwzRaRz+FGcwhsH4wlmJFBnEhaSTcriclSdsAjQFMBfTE17YeJ7kItSxUllrqQTnZYJDrscfsMruvUn5vpMCKRBd2n5q7xGKuJvhodszmNBQS7U990iJacDe71vYKCNz833JG7TG10c3dvPnK+bowM7l8AGkCET1fZHGUxGA48ZMUpX6n88RiE4rBe0NrMSXLWV45HVJL5Lx/tf0Qpzfl6nd6eegix1oKZx6lQePmKrOL2v0bfaCHz7Kf8ydr8fYVB7y64sYxg37N0P1 rI1LZ0Rb 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 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 Tue, Apr 29, 2025 at 10:41:27AM +0100, Lorenzo Stoakes wrote: >On Tue, Apr 29, 2025 at 11:38:23AM +0200, David Hildenbrand wrote: >> On 29.04.25 11:31, Lorenzo Stoakes wrote: >> > Wei, >> > >> > NACK the whole series. >> > >> > I'm really not sure how to get through to you. You were _explicitly_ >> > advised not to send this series. And yet you've sent it anyway. >> > >> > I mean, I appreciate your enthusiasm and the fact you've made tests here >> > etc. obviously. And you've clearly put a TON of work in. But I just don't >> > know why you would when explicitly told not to without at least discussing >> > it first? >> > >> > This just isn't a great way of interacting with the community. We're all >> > human, please try to have some empathy for others here, as I really do try >> > to have with you as best I can. >> > >> > This adds a ton of churn and LOCKS IN assumptions about how anon_vma works, >> > clashes with other series (most notably series I've been working on), takes >> > away from efforts I want to make to start to join file-backed and anon >> > reverse mapping logic, separates the two in such a way as to encourage this >> > to nonly grow and generally isn't conducive to where I want to go with >> > rmap. >> >> anon_vma, the unloved child. :) >> >> I would love to see a simplification that makes it less special, and I can >> understand how adding tests for the ways it is special can be >> counter-productive. >> >> > >> > This is part of why I explicitly told you please don't go down this road, >> > because you're likely to end up doing work that doesn't get used. It's not >> > a great use of your time either. >> > >> > Since there's something useful here in tests, I may at a later date come >> > back to those. >> >> Agreed, skimming over the tests there are some nice diagrams and cases. >> >> But I would hope that for most of these cases we could test on a higher >> level: test our expectations when running real programs that we want to >> check, especially when performing internal changes on how we handle anon >> memory + rmap. >> >> E.g., do fork(), then test if we can successfully perform rmap >> lookups/updates (e.g., migrate folio to a different numa node etc). >> > >That's a great point! Wei - if you could look at making some self-tests >(i.e. that live in tools/testing/selftests/mm) that try to recreate _real_ >scenarios that use the rmap like this and assert correct behaviour there, >that could be a positive way of moving forward with this. > I am trying to understand what scenarios you want. Something like below? * fork and migrate a range in child * fork/unmap in parent and migrate a range in child If the operation is successful, then we are good, right? >We'd be absolutely happy to take patches like that! > >> -- >> Cheers, >> >> David / dhildenb >> >> > >Cheers, Lorenzo -- Wei Yang Help you, Help me