{"thread":{"id":"62891","subject":"\"meson test\" very slow on Windows","startedAt":"2025-02-01T22:57:34Z","lastAt":"2025-02-02T23:13:57Z","messageCount":5,"participants":["M Hickford","Johannes Sixt","Patrick Steinhardt","brian m. carlson"],"isPatch":false,"patchVersion":null,"patchTotal":null},"messages":[{"id":"511649","messageId":"CAGJzqsmmq1R9_q=p_AsuFMFr3UzyQ4H186CpfWTnCoAnHu_OXA@mail.gmail.com","threadId":"62891","inReplyTo":null,"subject":"\"meson test\" very slow on Windows","fromName":"M Hickford","fromEmail":"mirth.hickford@gmail.com","sentAt":"2025-02-01T22:56:53Z","receivedAt":"2025-02-01T22:57:34Z","isPatch":false,"sender":{"key":"mirth.hickford@gmail.com","avatar":"https://avatars.githubusercontent.com/u/105314?v=4"},"body":"Hi. Has anyone else found that \"meson test\" is very slow on Windows? I\nbuilt Git using \"meson compile\" with compiler MSVC and backend ninja.\n\nCuriously the first few tests were fast. Test 20 (exact number varies)\nand later were slow:\n\n 1/1029 unit-tests OK\n 2.11s\n 2/1029 t-example-decorate OK\n 1.45s\n 3/1029 t-hash OK\n 1.32s\n 4/1029 t-hashmap OK\n 1.24s\n 5/1029 t-mem-pool OK\n 1.16s\n 6/1029 t-oid-array OK\n 1.10s\n 7/1029 t-oidmap OK\n 1.05s\n 8/1029 t-oidtree OK\n 0.98s\n 9/1029 t-prio-queue OK\n 0.94s\n 10/1029 t-reftable-basics OK\n 0.89s\n 11/1029 t-reftable-block OK\n 0.83s\n 12/1029 t-reftable-merged OK\n 0.77s\n 13/1029 t-reftable-pq OK\n 0.72s\n 14/1029 t-reftable-reader OK\n 0.64s\n 15/1029 t-reftable-readwrite OK\n 0.54s\n 16/1029 t-reftable-record OK\n 0.45s\n 17/1029 t-reftable-tree OK\n 0.29s\n 18/1029 t-strbuf OK\n 0.20s\n 19/1029 t-strcmp-offset OK\n 0.51s\n 20/1029 t-trailer OK\n 5.40s\n 21/1029 t-urlmatch-normalization OK\n 5.32s\n 22/1029 t-reftable-stack OK\n 17.67s\n 23/1029 t0013-sha1dc OK\n 42.50s\n 24/1029 t0004-unwritable OK\n 46.87s\n 25/1029 t0022-crlf-rename OK\n 43.77s\n 26/1029 t0014-alias OK\n 49.05s\n 27/1029 t0023-crlf-am OK\n 32.28s\n 28/1029 t0005-signals OK\n 49.83s\n 29/1029 t0018-advice OK\n 58.71s\n 30/1029 t0010-racy-git OK\n 64.75s\n\nOn Linux, all tests were fast as expected.\n\nI built at commit 58b5801aa9 (The sixth batch, 2025-01-31)\n\nAny ideas?\n"},{"id":"511653","messageId":"89612095-6b10-44a1-a29c-b143d67ce7da@kdbg.org","threadId":"62891","inReplyTo":"CAGJzqsmmq1R9_q=p_AsuFMFr3UzyQ4H186CpfWTnCoAnHu_OXA@mail.gmail.com","subject":"Re: \"meson test\" very slow on Windows","fromName":"Johannes Sixt","fromEmail":"j6t@kdbg.org","sentAt":"2025-02-02T07:46:46Z","receivedAt":"2025-02-02T07:46:55Z","isPatch":false,"sender":{"key":"j6t@kdbg.org","avatar":"https://avatars.githubusercontent.com/u/14810926?v=4"},"body":"Am 01.02.25 um 23:56 schrieb M Hickford:\n> Hi. Has anyone else found that \"meson test\" is very slow on Windows? I\n> built Git using \"meson compile\" with compiler MSVC and backend ninja.\n\nThe tests are very slow on Windows in general. Please clarify: when you\nsay \"very slow on Windows with meson\", do you then mean \"slower than\nwith a Makefile build\"?\n\n-- Hannes\n\n"},{"id":"511656","messageId":"Z59TzBKLHQJwXUBJ@pks.im","threadId":"62891","inReplyTo":"89612095-6b10-44a1-a29c-b143d67ce7da@kdbg.org","subject":"Re: \"meson test\" very slow on Windows","fromName":"Patrick Steinhardt","fromEmail":"ps@pks.im","sentAt":"2025-02-02T11:15:24Z","receivedAt":"2025-02-02T11:15:31Z","isPatch":false,"sender":{"key":"ps@pks.im","avatar":"https://avatars.githubusercontent.com/u/4056630?v=4"},"body":"On Sun, Feb 02, 2025 at 08:46:46AM +0100, Johannes Sixt wrote:\n> Am 01.02.25 um 23:56 schrieb M Hickford:\n> > Hi. Has anyone else found that \"meson test\" is very slow on Windows? I\n> > built Git using \"meson compile\" with compiler MSVC and backend ninja.\n> \n> The tests are very slow on Windows in general.\n\nYeah, it's an unfortunate reality that tests are slow on Windows. It was\nalso mentioned that the first ~20 tests are fast. This is expected,\nbecause the unit tests execute first, and these are way faster compared\nto the integration tests.\n\n> Please clarify: when you say \"very slow on Windows with meson\", do you\n> then mean \"slower than with a Makefile build\"?\n\nJudging from my own tests there is no significant difference between the\ntwo build systems. But in case there is I'd be happy to learn about it.\n\nPatrick\n"},{"id":"511664","messageId":"CAGJzqsmo988VwABNgozwQEKBe-nyfw9f2G2obygqs8OtuYpeiQ@mail.gmail.com","threadId":"62891","inReplyTo":"89612095-6b10-44a1-a29c-b143d67ce7da@kdbg.org","subject":"Re: \"meson test\" very slow on Windows","fromName":"M Hickford","fromEmail":"mirth.hickford@gmail.com","sentAt":"2025-02-02T21:45:34Z","receivedAt":"2025-02-02T21:46:12Z","isPatch":false,"sender":{"key":"mirth.hickford@gmail.com","avatar":"https://avatars.githubusercontent.com/u/105314?v=4"},"body":"On Sun, 2 Feb 2025 at 07:46, Johannes Sixt wrote:\n>\n> Am 01.02.25 um 23:56 schrieb M Hickford:\n> > Hi. Has anyone else found that \"meson test\" is very slow on Windows? I\n> > built Git using \"meson compile\" with compiler MSVC and backend ninja.\n>\n> The tests are very slow on Windows in general. Please clarify: when you\n> say \"very slow on Windows with meson\", do you then mean \"slower than\n> with a Makefile build\"?\n\nThanks, I didn't know about that. This is my first time I've\nsuccessfully built Git on Windows, so I can't compare build systems.\n(Makefile and CMake never worked for me.)\n\nOut of curiosity, why are the integration tests so much slower on\nWindows than Linux? Is it the 10+ ms overhead of creating each new\nprocess? https://stackoverflow.com/q/47845/284795\nhttps://stackoverflow.com/questions/10710912/what-is-the-process-creation-overhead-in-windows\n"},{"id":"511667","messageId":"Z5_8MuRxJKZm2bdH@tapette.crustytoothpaste.net","threadId":"62891","inReplyTo":"CAGJzqsmo988VwABNgozwQEKBe-nyfw9f2G2obygqs8OtuYpeiQ@mail.gmail.com","subject":"Re: \"meson test\" very slow on Windows","fromName":"brian m. carlson","fromEmail":"sandals@crustytoothpaste.net","sentAt":"2025-02-02T23:13:54Z","receivedAt":"2025-02-02T23:13:57Z","isPatch":false,"sender":{"key":"sandals@crustytoothpaste.net","avatar":"https://avatars.githubusercontent.com/u/497054?v=4"},"body":"On 2025-02-02 at 21:45:34, M Hickford wrote:\n> On Sun, 2 Feb 2025 at 07:46, Johannes Sixt wrote:\n> >\n> > Am 01.02.25 um 23:56 schrieb M Hickford:\n> > > Hi. Has anyone else found that \"meson test\" is very slow on Windows? I\n> > > built Git using \"meson compile\" with compiler MSVC and backend ninja.\n> >\n> > The tests are very slow on Windows in general. Please clarify: when you\n> > say \"very slow on Windows with meson\", do you then mean \"slower than\n> > with a Makefile build\"?\n> \n> Thanks, I didn't know about that. This is my first time I've\n> successfully built Git on Windows, so I can't compare build systems.\n> (Makefile and CMake never worked for me.)\n> \n> Out of curiosity, why are the integration tests so much slower on\n> Windows than Linux? Is it the 10+ ms overhead of creating each new\n> process? https://stackoverflow.com/q/47845/284795\n> https://stackoverflow.com/questions/10710912/what-is-the-process-creation-overhead-in-windows\n\nOur tests are primarily written in shell, which does a lot of fork and\nexec. These are native to and highly optimized on Unix, but Windows\ndoesn't have this functionality natively for Win32 programs and the\nemulation is slow. Part of that is because the Cygwin-based libc\nactually has to emulate it nearly perfectly for software to work. While\na partial emulation might work in _some_ cases, it would break in\nothers, so a lot of care and expense has to be provided in making it\nwork just so.\n\nWindows _does_ have this functionality in the kernel and it is\nreasonably performant, but it's only available in the Linux subsystem\nand not in the Win32 subsystem. The tests will probably be much faster\nif you use WSL, although that wouldn't allow you to build a Windows\nbinary.\n\nDscho and others put a lot of effort into porting shell programs into C\nto make them more performant on Windows (and elsewhere), since this has\nbeen a problem for a long time.\n-- \nbrian m. carlson (they/them or he/him)\nToronto, Ontario, CA\n"}]}