Osmo io » History » Version 7
laforge, 03/14/2024 08:05 AM
some more background info.
| 1 | 1 | laforge | h1. osmo_io |
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| 2 | |||
| 3 | 3 | laforge | @osmo_io@ is the new (2023) way of ho we do I/O in osmocom projects. It moves from a raw select/poll abstraction (where every application performs its own read/write once the fd becomes readble/writable) to a submission/completion model, where the actual I/O is performed by the library, an the application just submits write requests (as @struct msgb@) and receives write-completion and read-completion call-backs. |
| 4 | 1 | laforge | |
| 5 | 7 | laforge | Apart from having more code reuse and a cleaner split between application and I/O library, this has the added advantage that the underlying operating system I/O mechanism can be swapped out without touching each and every application. Specifically, we have currently the following two back-ends implemented in libosmocore: |
| 6 | * *POLL*: classic osmo_fd based implementation using @poll(2)@ (default) |
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| 7 | * *IO_URING*: a backend using the Linux kernel @io_uring(7)@ API |
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| 8 | 1 | laforge | |
| 9 | 7 | laforge | The choice of back-end is done via setting the @LIBOSMO_IO_BACKEND@ environment variable. If you set it to IO_URING when starting an osmocom program, all sub-systems / interfaces ported over to the osmo_io API will make use of the @io_uring(7)@ API (via liburing). |
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| 11 | The main advantage of io_uring is performance. Benchmarking has shown that a classic, poll-based production osmo-bsc loaded with 400 TRX is spending about 40% of its CPU cycles in the system call overhad (sock_poll, tcp_poll and do_sys_poll) and a lot of system call entry/exit in general, due to the many small read/write/recvmsg/sendmsg/recfrom/sendto and poll calls. |
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| 12 | |||
| 13 | For more information, see: |
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| 14 | * the original discussion in #5751 |
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| 15 | * FIXME |
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| 16 | |||
| 17 | 3 | laforge | API reference at https://ftp.osmocom.org/api/latest/libosmocore/core/html/osmo__io_8c.html#details |
| 18 | |||
| 19 | 1 | laforge | h2. Implementation status |
| 20 | |||
| 21 | 2 | laforge | The below tables indicate the implementation status of the osmo_io migration: |
| 22 | 1 | laforge | |
| 23 | 2 | laforge | h3. Libraries |
| 24 | |||
| 25 | 6 | laforge | |_.library/interface|_.protocol|_.transport|_.users|_.commit|_.issue| |
| 26 | |libosmocore|gsmtap|UDP|everyone|"libosmocore":https://gerrit.osmocom.org/c/libosmocore/+/34743|#6213| |
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| 27 | |libosmo-mgcp-client|MGCP|UDP|osmo-bsc, osmo-msc, osmo-hnbgw|"osmo-mgw":https://gitea.osmocom.org/cellular-infrastructure/osmo-mgw/commit/8b524c9151177d681b35332146d7628fafd82846|#5754| |
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| 28 | |libosmogb ns2|NS|UDP|osmo-pcu, osmo-gbproxy, osmo-sgsn|"libosmocore":https://gitea.osmocom.org/osmocom/libosmocore/commit/eb9edbab54463cb705ec7b770e022a215ce503c7|#5751| |
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| 29 | |libosmo-netif|stream_cli|TCP|libosmo-sigtran(ipa), osmo-bsc(cbsp), osmo-cbc(cbsp)|"libosmo-netif":https://gitea.osmocom.org/osmocom/libosmo-netif/commit/0e7028f742dedefd9fccc2d5b26875fca4036f58|#5753| |
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| 30 | |libosmo-netif|stream_cli|SCTP|libosmo-sigtran|"libosmo-netif":https://gitea.osmocom.org/osmocom/libosmo-netif/commit/7e6d2e0f99ff095f4714f03b1ed991d6c9cb9c61|#5753| |
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| 31 | |libosmo-sigtran|xUA ASP (SUA, M3UA)|SCTP|osmo-bsc, osmo-msc, osmo-sgsn, osmo-hnbgw, osmo-smlc|"libosmo-sigtran":https://gitea.osmocom.org/osmocom/libosmo-sccp/commit/9257cd896e255403822bee6f87f5487a92fd3c11|#5752| |
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| 32 | 2 | laforge | |
| 33 | h3. Program |
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| 34 | |||
| 35 | 6 | laforge | |_.program|_.Interface/protocol|_.transport|_.commit|_.issue| |
| 36 | 2 | laforge | |osmo-gbproxy|Gb/NS|UDP|indirect via "libosmogb ns2":https://gitea.osmocom.org/osmocom/libosmocore/commit/eb9edbab54463cb705ec7b770e022a215ce503c7| |
| 37 | 6 | laforge | |osmo-bsc|CBSP|TCP client+server|"osmo-bsc":https://gitea.osmocom.org/cellular-infrastructure/osmo-bsc/commit/85687bf176e4b9663f2396a27c28b49221c72fa3|#6170| |
| 38 | 2 | laforge | |osmo-bsc|meas_feed|UDP|"osmo-bsc":https://gitea.osmocom.org/cellular-infrastructure/osmo-bsc/commit/ea388e1db1465afdcfd2796336732d29d80a2b9f| |
| 39 | 6 | laforge | |osmo-bsc|MGCP|UDP|indirect via libosmo-mgcp-client|#5755| |
| 40 | |osmo-bsc|M3UA/SUA/IPA|SCTP/TCP|indirect via libosmo-sigtran|#5755| |
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| 41 | 1 | laforge | |osmo-hnbgw|MGCP|UDP|indirect via libosmo-mgcp-client| |
| 42 | 4 | laforge | |osmo-hnbgw|M3UA/SUA/IPA|SCTP/TCP|indirect via libosmo-sigtran| |
| 43 | 1 | laforge | |osmo-msc|MGCP|UDP|indirect via libosmo-mgcp-client| |
| 44 | 4 | laforge | |osmo-msc|M3UA/SUA/IPA|SCTP/TCP|indirect via libosmo-sigtran| |
| 45 | |osmo-sgsn|M3UA/SUA/IPA|SCTP/TCP|indirect via libosmo-sigtran| |
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| 46 | |osmo-sgsn|Gb/NS|UDP|indirect via "libosmogb ns2":https://gitea.osmocom.org/osmocom/libosmocore/commit/eb9edbab54463cb705ec7b770e022a215ce503c7| |
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| 47 | 1 | laforge | |osmo-smlc|M3UA/SUA/IPA|SCTP/TCP|indirect via libosmo-sigtran| |
| 48 | |osmo-stp|M3UA/SUA/IPA|SCTP/TCP|indirect via libosmo-sigtran|#5752| |
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| 49 | 7 | laforge | |
| 50 | h2. Further reading |
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| 51 | |||
| 52 | * "wikipedia page on io_uring":https://en.wikipedia.org/wiki/Io_uring |
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| 53 | * "Efficient IO with io_uring":https://kernel.dk/io_uring.pdf by the io_uring creator Jens Axboe. |
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| 54 | * "io_uring and networking in 2023":https://kernel.dk/io_uring%20and%20networking%20in%202023.pdf |
