# [RFC] [Discussion] A new JIT implementation based on IR Framework - Thread: https://externals.io/message/121108 - Original archive: https://news-web.php.net/php.internals/121108 - Started by Dmitry Stogov on 2023-09-21T08:26:34+00:00 - Messages: 9 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #121108 — Dmitry Stogov — 2023-09-21T08:26:34+00:00 URL: https://externals.io/message/121108#121108 Hi Internals, After all the Poll Request discussions (see https://github.com/php/php-src/pull/12079), code-reviews and internal discussions with core developers we decided to move this through the RFC process. Thanks to all participants. The RFC is open for discussion: https://wiki.php.net/rfc/jit-ir Thanks. Dmitry. --- ## #121109 — tim@bastelstu.be — 2023-09-21T09:13:14+00:00 URL: https://externals.io/message/121108#121109 · In reply to: #121108 Hi > After all the Poll Request discussions (see > https://github.com/php/php-src/pull/12079), code-reviews and internal > discussions with core developers we decided to move this through the RFC > process. > > Thanks to all participants. > > The RFC is open for discussion: https://wiki.php.net/rfc/jit-ir Thank you. I find it important to follow the formal process, even if many folks are not able to make a meaningful decision due to the lack of knowledge about the topic. This includes me. That said, I'd like to add my two cents to the "Open Issues" section: My understanding is that even if the new JIT might not (yet) be better than the old one, it is not worse and it is more maintainable. The reactions from more knowledgeable folks were pretty positive overall. So if the new JIT passes the existing test suite without issues, I don't see a reason why the old JIT should not be replaced right away. By immediately removing the old JIT (ideally in a separate commit) the codebase is cleaned up and users that want to test PHP 8.4 (or whatever that version may be in the end) will be forced to also test the new JIT which is probably a good thing. Best regards Tim Düsterhus --- ## #121110 — Sebastian Bergmann — 2023-09-21T09:21:59+00:00 URL: https://externals.io/message/121108#121110 · In reply to: #121109 Am 21.09.2023 um 11:13 schrieb Tim Düsterhus: > Thank you. I find it important to follow the formal process, even if many > folks are not able to make a meaningful decision due to the lack of > knowledge about the topic. This includes me. I'm in the same boat. > My understanding is that even if the new JIT might not (yet) be better > than the old one, it is not worse and it is more maintainable. The > reactions from more knowledgeable folks were pretty positive overall. That is my understanding as well. > So if the new JIT passes the existing test suite without issues, I don't > see a reason why the old JIT should not be replaced right away. By > immediately removing the old JIT (ideally in a separate commit) the > codebase is cleaned up and users that want to test PHP 8.4 (or whatever > that version may be in the end) will be forced to also test the new JIT > which is probably a good thing. I agree. As a sidenote: most of the teams that I work with use PHP 8 in production. However, none of them use the current JIT. It either caused problems (especially during early PHP 8.0 versions), or does not bring any significant performance improvement. Against that backdrop, I would be interested in whether you, Dmitry or Zend, can share some insight from real-world usage of the JIT. --- ## #121111 — Dmitry Stogov — 2023-09-21T09:25:42+00:00 URL: https://externals.io/message/121108#121111 · In reply to: #121109 Hi Tim. > Hi > > > > […] > > Thank you. I find it important to follow the formal process, even if > many folks are not able to make a meaningful decision due to the lack of > knowledge about the topic. This includes me. > > That said, I'd like to add my two cents to the "Open Issues" section: > > My understanding is that even if the new JIT might not (yet) be better > than the old one, it is not worse and it is more maintainable. The > reactions from more knowledgeable folks were pretty positive overall. > > So if the new JIT passes the existing test suite without issues, Passing test suites doesn't mean we couldn't have other problems. > I don't > see a reason why the old JIT should not be replaced right away. By > immediately removing the old JIT (ideally in a separate commit) > I'm going to agree to remove the old JIT and I like the idea of removing it in a separate commit. Thanks. Dmitry. > > Best regards > Tim Düsterhus --- ## #121112 — Deleu — 2023-09-21T09:31:22+00:00 URL: https://externals.io/message/121108#121112 · In reply to: #121109 > Hi > > > My understanding is that even if the new JIT might not (yet) be better > than the old one, it is not worse and it is more maintainable. The > reactions from more knowledgeable folks were pretty positive overall. > > So if the new JIT passes the existing test suite without issues, I don't > see a reason why the old JIT should not be replaced right away. By > immediately removing the old JIT (ideally in a separate commit) the > codebase is cleaned up and users that want to test PHP 8.4 (or whatever > that version may be in the end) will be forced to also test the new JIT > which is probably a good thing. > If I understand correctly, the only way to fallback to the JIT 1.0 implementation is by compiling PHP with a new introduced flag, so the JIT 2.0 needs to be opt-out. The RFC doesn't mention the configurations for new JIT (init settings) which makes me assume that they're exactly the same? If these assumptions are right, I think the matter of keeping or removing JIT 1.0 implementation is mostly a matter of what makes Dmitry more comfortable. Removing it straight-away might result in adding more pressure in getting bug fixes on the new one, while keeping it might make it possible for whoever is relying heavily on JIT to still compile new PHP releases with JIT 1.0 to give more time to iron out the final details on JIT 2.0. Of course this is a very basic analysis on my part which mixes my experience in replacing PHP running-systems with new rewrites and it's much more comfortable to me to have a fallback mechanism in place which may or may not be entirely relevant here. -- Marco Deleu --- ## #121113 — Dmitry Stogov — 2023-09-21T09:37:17+00:00 URL: https://externals.io/message/121108#121113 · In reply to: #121110 Hi Sebastian, On Thu, Sep 21, 2023 at 12:22 PM Sebastian Bergmann wrote: > Am 21.09.2023 um 11:13 schrieb Tim Düsterhus: > > […] > many > > […] > > I'm in the same boat. > > > […] > > That is my understanding as well. > > > […] > > I agree. > > As a sidenote: most of the teams that I work with use PHP 8 in production. > However, none of them use the current JIT. It either caused problems > (especially during early PHP 8.0 versions), or does not bring any > significant performance improvement. Against that backdrop, I would be > interested in whether you, Dmitry or Zend, can share some insight from > real-world usage of the JIT. > I still don't recommend using JIT for production without serious testing and benchmarking for each concrete case. If you see less than 5% speedup - you probably don't need JIT; if an AMPHP bsed server becomes 1.5 times faster it's a different story. Thanks. Dmitry. > -- > > To unsubscribe, visit: https://www.php.net/unsub.php --- ## #121114 — Dmitry Stogov — 2023-09-21T09:47:46+00:00 URL: https://externals.io/message/121108#121114 · In reply to: #121112 Hi Deleu, > > > > > > […] > > If I understand correctly, the only way to fallback to the JIT 1.0 > implementation is by compiling PHP with a new introduced flag, so the JIT > 2.0 needs to be opt-out. The RFC doesn't mention the configurations for new > JIT (init settings) which makes me assume that they're exactly the same? If > these assumptions are right, I think the matter of keeping or removing JIT > 1.0 implementation is mostly a matter of what makes Dmitry more > comfortable. Removing it straight-away might result in adding more pressure > in getting bug fixes on the new one, while keeping it might make it > possible for whoever is relying heavily on JIT to still compile new PHP > releases with JIT 1.0 to give more time to iron out the final details on > JIT 2.0. > In the current state the Pull Request starts using the new JIT implementation by default, but keeps the old implementation. It's a question, if we need to keep it for a while or remove it immediately. Now I think it's going to be removed in PR/RFC before starting the voting. > Of course this is a very basic analysis on my part which mixes my > experience in replacing PHP running-systems with new rewrites and it's much > more comfortable to me to have a fallback mechanism in place which may or > may not be entirely relevant here. > Keeping the disabled old JIT, we won't test it anyway and this won't guarantee anything. In case the new JIT will cause really serious problems we may consider reverting it. Thanks. Dmitry . > > -- > Marco Deleu --- ## #121234 — Dmitry Stogov — 2023-10-05T16:44:05+00:00 URL: https://externals.io/message/121108#121234 · In reply to: #121108 Hi Internals, I've published a presentation about the IR Framework design and implementation details. See https://www.researchgate.net/publication/374470404_IR_JIT_Framework_a_base_for_the_next_generation_JIT_for_PHP It explains many complex things in simple pictures. Thanks. Dmitry. On Thu, Sep 21, 2023 at 11:26 AM Dmitry Stogov wrote: > Hi Internals, > > After all the Poll Request discussions (see > https://github.com/php/php-src/pull/12079), code-reviews and internal > discussions with core developers we decided to move this through the RFC > process. > > Thanks to all participants. > > The RFC is open for discussion: https://wiki.php.net/rfc/jit-ir > > Thanks. Dmitry. --- ## #121235 — Paul Dragoonis — 2023-10-05T17:20:54+00:00 URL: https://externals.io/message/121108#121235 · In reply to: #121234 > Hi Internals, > > I've published a presentation about the IR Framework design and > implementation details. > See > > https://www.researchgate.net/publication/374470404_IR_JIT_Framework_a_base_for_the_next_generation_JIT_for_PHP > It explains many complex things in simple pictures. > Hi Dmitry, Thanks for helping explain things in graphical format. I will for sure study the material closely. As for the point around keeping the old JIT around as a safety measure and fallback. I think this is an excellent idea and may give good peace of mind and confidence for new adopters, that they can easily "switch back" to JIT 1.0 if any edge cases occur we didn't find yet in JIT 2.0, without waiting for future PHP releases (patches) to come out. It can be months before people get new patched PHP versions (think about centos or Debian distributions, or Docker images of PHP) Just like we've done with many things over the years, we first deprecated something and keep it in the language and in future release we remove it completely. Many thanks, Paul > Thanks. Dmitry. > > On Thu, Sep 21, 2023 at 11:26 AM Dmitry Stogov > wrote: > > > […]