{"action":"created","issue":{"url":"https://api.github.com/repos/JuliaLang/julia/issues/15740","repository_url":"https://api.github.com/repos/JuliaLang/julia","labels_url":"https://api.github.com/repos/JuliaLang/julia/issues/15740/labels{/name}","comments_url":"https://api.github.com/repos/JuliaLang/julia/issues/15740/comments","events_url":"https://api.github.com/repos/JuliaLang/julia/issues/15740/events","html_url":"https://github.com/JuliaLang/julia/issues/15740","id":145313197,"number":15740,"title":"Warning and slowdown for multithreaded Julia code","user":{"login":"kpamnany","id":3784427,"avatar_url":"https://avatars.githubusercontent.com/u/3784427?v=3","gravatar_id":"","url":"https://api.github.com/users/kpamnany","html_url":"https://github.com/kpamnany","followers_url":"https://api.github.com/users/kpamnany/followers","following_url":"https://api.github.com/users/kpamnany/following{/other_user}","gists_url":"https://api.github.com/users/kpamnany/gists{/gist_id}","starred_url":"https://api.github.com/users/kpamnany/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/kpamnany/subscriptions","organizations_url":"https://api.github.com/users/kpamnany/orgs","repos_url":"https://api.github.com/users/kpamnany/repos","events_url":"https://api.github.com/users/kpamnany/events{/privacy}","received_events_url":"https://api.github.com/users/kpamnany/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/JuliaLang/julia/labels/multi-threading","name":"multi-threading","color":"fbca04"},{"url":"https://api.github.com/repos/JuliaLang/julia/labels/performance","name":"performance","color":"d7e102"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":4,"created_at":"2016-04-02T00:02:56Z","updated_at":"2016-04-02T05:54:55Z","closed_at":null,"body":"Running our application (Celeste) with 8 threads or more produces the following warning (5 of them, sometimes 4):\r\n```\r\nWARNING: could not attach metadata for @simd loop.\r\n```\r\nAfter which performance gets completely hosed. This message doesn't appear (and performance doesn't get trashed) with 4 threads or less.\r\n\r\nSearches for this issue suggest this has something to do with inlining functions, but most of what I found related to package coverage testing which is not what I'm doing.\r\n\r\nIs there some issue with threads and this loop metadata?"},"comment":{"url":"https://api.github.com/repos/JuliaLang/julia/issues/comments/204652215","html_url":"https://github.com/JuliaLang/julia/issues/15740#issuecomment-204652215","issue_url":"https://api.github.com/repos/JuliaLang/julia/issues/15740","id":204652215,"user":{"login":"yuyichao","id":712232,"avatar_url":"https://avatars.githubusercontent.com/u/712232?v=3","gravatar_id":"","url":"https://api.github.com/users/yuyichao","html_url":"https://github.com/yuyichao","followers_url":"https://api.github.com/users/yuyichao/followers","following_url":"https://api.github.com/users/yuyichao/following{/other_user}","gists_url":"https://api.github.com/users/yuyichao/gists{/gist_id}","starred_url":"https://api.github.com/users/yuyichao/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/yuyichao/subscriptions","organizations_url":"https://api.github.com/users/yuyichao/orgs","repos_url":"https://api.github.com/users/yuyichao/repos","events_url":"https://api.github.com/users/yuyichao/events{/privacy}","received_events_url":"https://api.github.com/users/yuyichao/received_events","type":"User","site_admin":false},"created_at":"2016-04-02T05:54:55Z","updated_at":"2016-04-02T05:54:55Z","body":"From the version it seems that this should be affected by #15717 although that won't print a warning like this...\r\n\r\nI'm not really familiar with the threading front end but it may be helpful to see the typed ast (`@code_typed`) of the function for 4 threads and 8 threads.\r\n"}}