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[221.241.217.81]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-211d0f36cafsm13156335ad.149.2024.11.15.06.54.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Nov 2024 06:54:39 -0800 (PST) Date: Fri, 15 Nov 2024 23:54:34 +0900 Message-ID: From: Hajime Tazaki To: anton.ivanov@kot-begemot.co.uk Cc: johannes@sipsolutions.net, linux-um@lists.infradead.org, ricarkol@google.com, Liam.Howlett@oracle.com Subject: Re: [RFC PATCH v2 00/13] nommu UML In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/26.3 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241115_065442_185062_3A6B338E X-CRM114-Status: GOOD ( 15.61 ) X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org Hello Anton, thanks for the comment. On Fri, 15 Nov 2024 19:26:07 +0900, Anton Ivanov wrote: > > What do others think? Would you use it? What for? > > I always thought of it as "another LKL". In that case, it can be compared > to LKL on merit and if it is equivalent or better - go into kernel. > > If there is another use case, I will be glad to hear it. In a high-level view, the usage is different (no merit/demerit). LKL is used with userspace binaries, linked with, or dynamically replaced with the liblinux.so. LKL has a userspace API derived from syscall interface, which can be used to bridge LKL-world and host-kernel world (not specific to Linux host). This patchset (nommu UML) doesn't change the usage of current UML. In an internal implementation point of view, both (LKL and nommu-UML) uses !MMU. While LKL can be implemented with MMU-full configuration, we found (the last patch was back in 2021) that it is not trivial. LKL has no process model, currently only runs in a single (LKL) process. no vfork(2) support. nommu-UML can host multiple processes with vfork available. the patch size is: LKL (last v8 patch): mostly 5k lines of modifications nommu-UML: 1.2k lines of mods. I think it looks like similar (as I'm from LKL which also uses !MMU), but different from various aspects. let me know if you wish to see more about the comparison. -- Hajime