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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi everyone, The next proposed meeting is Monday, June 16th 10:00 - 12:00 CEST at https://meet.jit.si/MirageOS -- see our shared pad at https://pad.data.coop/To6IOSeNSOK9kFVlgo7XWw?both# for notes and agenda (add your talking points there) :) Below are the notes from the last meeting (June 2nd) Best, Hannes ## Meeting June 2nd 10:00 - 12:00 CEST - Participants: Pierre, Hannes, Virgile ### OCaml 5 performance - Virgile did some experiments in last 2024 about mirage-www and OCaml 5 - Notes about results (using OCaml 5.2): https://hackmd.io/@Firobe/ByKlnueNke - TL;DR: If set the space-overhead GC parameter to 60 (or 80), we get similar memory behaviour than OCaml 4 - "with OCaml 5, the GC parameters need to be tweaked" - with default space_overhead, there's ~2x CPU used; with space_overhead set to 60 (memory is 0.94x), 1.62x CPU is used - Pierre didn't measure the memory consumption with OCaml 5, the unikernel has 32MB assigned. The measure was throughput, and OCaml 5 was slightly better. - Virgile: from memories, the GC pacing is very bad under stress -- memory usage is exploding - Hannes: The compaction needs to be called manually (with OCaml5), so we need to figure places where to call it. - conversation about this on the Ocamllabs slack: https://hackmd.io/@Firobe/H19exkozxl - Pierre: Is compaction called from full_major? Virgile: No, it is not. - Pierre: when running a dns-resolver locally, there's quickly (after 10 - 20 minutes) an out of memory. This is due to a lot of Bigarray allocation. This is not only on OCaml 5. - Hannes: removing BAs is very desirable in general, but haven't been done yet mostly due to Xen which needs memory alignment - Hannes: availability of memory profiling tools will help figuring out the exact sources of the allocations and where efforts should be directed - Pierre: Didn't work too much on the io-page stuff. There's some bigarray usage in TCP/IP (checksum computation). Apart from that, it seems to be doable to get the io-page PR https://github.com/mirage/io-page/pull/72 merged. The cstruct-using-bytes branch works pretty nicely. - Hannes: about checksum computations, we can take the code in https://github.com/robur-coop/utcp/blob/main/src/checksum.ml which works for both bytes/string and Cstruct.t - Hannes will take a look and create a branch/PR for mirage-tcpip (under the assumption that Cstruct.t is backed by bytes) ### Unikraft - Virgile mentioned that this is mostly ready, there's a mail draft to be sent to the MirageOS mailing list - last bug to fix in network stack ### Security vulnerabilities - Hannes: will findings from hacksat challenge be reported to security@mirage.io - Virgile: Yes, all that are related to MirageOS, other open source findings will as well be upstreamed. - Hannes: when will you do that? At the time of when it is reported, or at the time the challenge ends? - Virgile: the current plan is to do that at the end. - Virgile: what is tested is one deployment of a HTTP/AF server. - Hannes: let's treat the 90 days period as a hard deadline to put out patches and reports From mirageos-devel-bounces@lists.xenproject.org Mon Jun 23 09:17:56 2025 Return-path: Envelope-to: archives@lists.xenproject.org Delivery-date: Mon, 23 Jun 2025 09:17:56 +0000 Received: from list by lists.xenproject.org with outflank-mailman.1022225.1397998 (Exim 4.92) (envelope-from ) id 1uTdJA-0007oV-8u; Mon, 23 Jun 2025 09:17:44 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1022225.1397998; Mon, 23 Jun 2025 09:17:44 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1uTdJA-0007oO-5L; Mon, 23 Jun 2025 09:17:44 +0000 Received: by outflank-mailman (input) for mailman id 1022225; Mon, 23 Jun 2025 09:17:42 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1uTdJ7-0007oI-Kr for mirageos-devel@lists.xenproject.org; Mon, 23 Jun 2025 09:17:42 +0000 Received: from mail.mehnert.org (mail.mehnert.org [213.73.89.200]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id e7a23772-5012-11f0-a30f-13f23c93f187; Mon, 23 Jun 2025 11:17:39 +0200 (CEST) Received: from [192.168.178.197] (pd95f5c6c.dip0.t-ipconnect.de [217.95.92.108]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "hannes@mehnert.org", Issuer "mehnert root CA" (not verified)) by mail.mehnert.org (Postfix) with ESMTPS id 8EC091881F for ; Mon, 23 Jun 2025 11:17:36 +0200 (CEST) X-BeenThere: mirageos-devel@lists.xenproject.org List-Id: Developer list for MirageOS List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: mirageos-devel-bounces@lists.xenproject.org Precedence: list Sender: "MirageOS-devel" X-Inumbo-ID: e7a23772-5012-11f0-a30f-13f23c93f187 DKIM-Signature: v=1; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Dear everybody, last week we had a nice discussion. The next one is in one week (June 30th 10:00 - 12:00 CEST at https://meet.jit.si/MirageOS -- see our shared pad at https://pad.data.coop/To6IOSeNSOK9kFVlgo7XWw?both# for notes and agenda (add your talking points there) :)) Below are the notes from last week. Best, Hannes ## Meeting June 16th 10:00 - 12:00 CEST - Participants: Pierre, Reynir, Hannes, Sam ### IO-page without Cstruct, and Cstruct.t without Bigarray - Pierre: have a branch with no bigarray in mirage-tcpip (see https://github.com/hannesm/mirage-tcpip/tree/no-bigarray) ``` cstruct.6.2.0 git git+https://github.com/hannesm/ocaml-cstruct.git#no-bigarray cstruct-lwt.6.2.0 git git+https://github.com/hannesm/ocaml-cstruct.git#no-bigarray io-page.3.0.0 git git+file:///home/user/mirage/io-page#no-cstruct mirage-net-xen.2.1.5 git git+file:///home/user/mirage/mirage-net-xen#io-page-ba mirage-xen.9.0.0 git git+file:///home/user/mirage/mirage-xen#new-iopage shared-memory-ring.3.2.1 git git+file:///home/user/mirage/shared-memory-ring#new-iopage shared-memory-ring-lwt.3.2.1 git git+file:///home/user/mirage/shared-memory-ring#new-iopage tcpip.9.0.1 (uninstalled) git git+https://github.com/hannesm/mirage-tcpip.git#no-bigarray vchan.6.0.2 git git+file:///home/user/mirage/ocaml-vchan#update-iopage-api vchan-xen.6.0.2 git git+file:///home/user/mirage/ocaml-vchan#update-iopage-api xen-gnt.4.0.2 (uninstalled) git git+file:///home/user/mirage/ocaml-gnt#new-iopage ``` ``` [2025-06-16 10:00:52] | ___| [2025-06-16 10:00:52] __| _ \ | _ \ __ \ [2025-06-16 10:00:52] \__ \ ( | | ( | ) | [2025-06-16 10:00:52] ____/\___/ _|\___/____/ [2025-06-16 10:00:52] Solo5: Bindings version v0.9.1 [2025-06-16 10:00:52] Solo5: Memory map: 32 MB addressable: [2025-06-16 10:00:52] Solo5: reserved @ (0x0 - 0xfffff) [2025-06-16 10:00:52] Solo5: text @ (0x100000 - 0x498fff) [2025-06-16 10:00:52] Solo5: rodata @ (0x499000 - 0x55afff) [2025-06-16 10:00:52] Solo5: data @ (0x55b000 - 0x8e4fff) [2025-06-16 10:00:52] Solo5: heap >= 0x8e5000 < stack < 0x2000000 [2025-06-16 10:00:52] 2025-06-16T08:00:52-00:00: [INFO] [net-xen frontend] connect 0 [2025-06-16 10:00:52] 2025-06-16T08:00:52-00:00: [INFO] [qubes.db] connecting to server... [2025-06-16 10:00:52] 2025-06-16T08:00:52-00:00: [INFO] [qubes.db] connected [2025-06-16 10:00:52] 2025-06-16T08:00:52-00:00: [INFO] [net-xen frontend] create: id=0 domid=1 [2025-06-16 10:00:52] 2025-06-16T08:00:52-00:00: [INFO] [net-xen frontend] sg:true gso_tcpv4:true rx_copy:true rx_flip:false smart_poll:false [2025-06-16 10:00:52] 2025-06-16T08:00:52-00:00: [INFO] [net-xen frontend] MAC: 00:16:3e:5e:6c:00 [2025-06-16 10:00:53] 2025-06-16T08:00:53-00:00: [INFO] [ethernet] Connected Ethernet interface 00:16:3e:5e:6c:00 [2025-06-16 10:00:53] 2025-06-16T08:00:53-00:00: [INFO] [ipv6] IP6: Starting [2025-06-16 10:00:53] 2025-06-16T08:00:53-00:00: [INFO] [ARP] Sending gratuitous ARP for 10.137.0.27 (00:16:3e:5e:6c:00) [2025-06-16 10:00:53] Fatal error: exception Invalid_argument("String.blit / Bytes.blit_string") [2025-06-16 10:00:53] Raised at Stdlib.invalid_arg in file "stdlib.ml", line 30, characters 20-45 [2025-06-16 10:00:53] Called from Ethernet__Ethernet_packet.Marshal.unsafe_fill in file "duniverse/ethernet/src/ethernet_packet.ml", line 63, characters 4-67 [2025-06-16 10:00:53] Called from Stdlib__Result.map in file "result.ml", line 25, characters 32-37 [2025-06-16 10:00:53] Called from Ethernet.Make.write.fill in file "duniverse/ethernet/src/ethernet.ml", line 107, characters 14-60 [2025-06-16 10:00:53] Called from Frontend.Make.write_already_locked.(fun) in file "duniverse/mirage-net-xen/lib/frontend.ml", line 304, characters 18-60 [2025-06-16 10:00:53] Called from Lwt.Sequential_composition.try_bind in file "duniverse/lwt/src/core/lwt.ml", line 2139, characters 10-14 [2025-06-16 10:00:53] Re-raised at Lwt.Miscellaneous.poll in file "duniverse/lwt/src/core/lwt.ml", line 3123, characters 20-29 [2025-06-16 10:00:53] Called from Xen_os__Main.run.aux in file "duniverse/mirage-xen/lib/main.ml", line 37, characters 10-20 [2025-06-16 10:00:53] Called from Dune__exe__Main.run in file "mirage/main.ml", line 4, characters 12-29 [2025-06-16 10:00:53] Called from Dune__exe__Main in file "mirage/main.ml", line 436, characters 2-7 [2025-06-16 10:00:53] Solo5: solo5_exit(2) called ``` - The issue is likely in mirage-net-xen passing a (too) small buffer to Ethernet, since the source location is a blit of the destination mac address (at offset 0 into the buffer) - Pierre: need to also investigate performance, since with the Cstruct using bytes does more copying - Hannes: I'm really happy this is moving forward. - Hannes: the ethernet implementation calls `Netif.write`, which calls the (mirage-net-xen) Frontend.write with the `~size` parameter, which then calls `write_no_retry`, which calls `write_already_locked` (`Cstruct.sub`) -- and I guess we should printf the `~size` parameter for further debugging - Hannes: in (mirage-net-xen) `write_already_locked` we call `fillf (Cstruct.sub cs_shared_block 0 size)` - Hannes: in (ethernet): `let size = eth_hdr_size + size` - Hannes: I'd recommend to printf the `size` - Pierre: there's some too small buffer passed somewhere - Hannes: I'm really happy to see this moving forward. The blocker in Mirleft was clearly the hanging of qubesdb/xen vchan. I'd love to think further about performance, and it seems the roadblock is lifted now :) ### Unikraft - Sam: The ocaml-unikraft package family has been released to the opam-repository - Virgile told that opam-monorepo is complaining with how the ocaml-unikraft packages are setup - Sam: we have patches for the mirage tool, also for net, block, time, etc. - we try to fix the small issues that are left, and it will be ready soon! - Hannes: did you do any further benchmarking? - Sam: not yet, there was a small bug: there are some extra bytes in each packet - unclear where they are coming from. we can safely just ignore them, they are always null bytes. - Sam: we plan to run again some benchmarks this week, and hope is that they'll be reasonably good - Pierre: in the end, it will be a potential replacement for solo5? - Sam: exactly, it is an alternative backend. for unikraft, you don't need solo5 tenders - you can run on qemu and firecracker. they have experimental ports for other backends they are working on. - Pierre: would it be possible to use with xen and qubes, or not? - Sam: unikraft has a backend for xen, but we didn't add it to the other layers - since I don't have a path to test it - Sam: I didn't write the code to generate the xen backend (in ocaml-unikraft) - Pierre: would be interesting, esp. if it delivers better performance - Hannes: which network stack do you use? - Sam: we initially used the unikraft one (which uses lwip), but now we use the OCaml one - Hannes: any news on multiple CPUs in unikraft? - Sam: not yet. it is on their roadmap. it is not in any released version. in some parts of the code I needed to debug, it is clear that it is monocore - Hannes: what is unikraft currently working on? do they have users? - Sam: they created a company to smoothen the deployment experience (unikraft cloud) - Hannes: I'm really happy you're pushing this work forward, so we can piggyback on the unikraft cloud, and at the same time we can evaluate the performance issues from their website (where solo5 is really slow), and figure out whether the performance is lost in solo5 or OCaml. ### OCaml compiler and cross-compiling - Sam: The OCaml 5.5 will include the patches needed for cross-compiling, so we don't need any further patches \o/ (apart from setting the number of domains to 1) - Hannes: For OCaml 5.4, do we have a patchset? - Sam: there's only a single PR left (to enable freestanding target), will open a PR on ocaml-solo5 and ocaml-unikraft when 5.4 is released - Hannes: from the OCaml release schedule, 5.4 is expected this summer (August) ### OxCaml - JaneStreet published their OxCaml project (including stack allocation, etc.) at https://oxcaml.org - MirageOS could use Oxcaml - it includes as well flambda2 - It would be interesting / nice to test the various compilers: - OCaml, OCaml with flambda1, OxCaml (with plain opam packages), OxCaml with annotated packages (to use e.g. stack allocation) - Sam: it is unclear how to use OxCaml with MirageOS, they seem to be based on the 5.2.0 compiler - and there would be various cross-compiling PRs needed to use OxCaml inside of MirageOS - Sam: unclear whether it is worth to backpatch OxCaml, or wait until they move to OCaml 5.3.0 or even 5.4.0. Maybe we'll find someone who has an idea of their roadmap. - Sam: it shouldn't be too hard to get something working, but it would be more work to upstream clean patches as merged.