From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-2.7 required=3.0 tests=AWL,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS shortcircuit=no autolearn=no autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id EC52C1F463 for ; Sun, 24 Nov 2019 21:56:56 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 67EAA1209C9; Mon, 25 Nov 2019 06:56:46 +0900 (JST) Received: from o1678948x4.outbound-mail.sendgrid.net (o1678948x4.outbound-mail.sendgrid.net [167.89.48.4]) by neon.ruby-lang.org (Postfix) with ESMTPS id 73C7D120953 for ; Mon, 25 Nov 2019 06:56:44 +0900 (JST) Received: by filter0046p3iad2.sendgrid.net with SMTP id filter0046p3iad2-28912-5DDAFC9F-9 2019-11-24 21:56:47.463171665 +0000 UTC m=+425214.588794084 Received: from herokuapp.com (unknown [3.87.184.74]) by ismtpd0002p1iad1.sendgrid.net (SG) with ESMTP id jZKB5vQ-QSSyQaWK9skyIw for ; Sun, 24 Nov 2019 21:56:47.377 +0000 (UTC) Date: Sun, 24 Nov 2019 21:56:47 +0000 (UTC) From: eregontp@gmail.com Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 71560 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 16188 X-Redmine-Issue-Author: Eregon X-Redmine-Issue-Assignee: jeremyevans0 X-Redmine-Sender: Eregon X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?KippOI8ZHtTweq7XfQzW93937kJ4QNWwSBuHnaMEcr37RjBjlZMJfjTs55scAq?= =?us-ascii?Q?RN7VofQa2YzvTZ6PBx1wIbGQLvdZA0CgryKtHve?= =?us-ascii?Q?gZ55BMGdSBC=2FJqGDIp5HUwixkRDBoSWg828o6fU?= =?us-ascii?Q?PaO1CWtC847=2FIEHz0Oh4G8fcnmLVsM6R8z2dYqo?= =?us-ascii?Q?6HymmrdfKuVfeEKuvK8k21KrPVj0dMT1mHw=3D=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 95926 Subject: [ruby-core:95926] [Ruby master Misc#16188] What are the performance implications of the new keyword arguments in 2.7 and 3.0? X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #16188 has been updated by Eregon (Benoit Daloze). I also measured on TruffleRuby, and there the diff is minimal, just adding the `ruby2_keywords` check on *splat call sites: https://github.com/oracle/truffleruby/commit/d143af3626aae009e2414bfe61833565fe3a0476 The results are similar (details on https://gist.github.com/eregon/15ebe02ff8f42c0ab964e1066a783f9d): * req: 4.6% slower * kw: 10.4% slower * kwrest: 10.9% slower In summary, I see about 10% slowdown on this micro benchmark, representative of `foo(*args)` calls, just by the extra `ruby2_keywords` check. ---------------------------------------- Misc #16188: What are the performance implications of the new keyword arguments in 2.7 and 3.0? https://bugs.ruby-lang.org/issues/16188#change-82766 * Author: Eregon (Benoit Daloze) * Status: Open * Priority: Normal * Assignee: jeremyevans0 (Jeremy Evans) ---------------------------------------- In #14183, keyword arguments became further separated from positional arguments. Contrary to the original design though, keyword and positional arguments are not fully separated for methods not accepting keyword arguments. Example: `foo(key: :value)` will `def foo(hash)` will pass a positional argument. This is of course better for compatibility, but I wonder what are the performance implications. The block argument is completely separate in all versions, so no need to concern ourselves about that. In Ruby <= 2.6: * The caller never needs to know about the callee's arguments, it can just take all arguments and pass them as an array. The last argument might be used to extract keyword, but this is all done at the callee side. * Splitting kwargs composed of Symbol and non-Symbol keys can be fairly expensive, but it is a rare occurrence. If inlining the callee and kwargs are all passed as a literal Hash at the call site, there shouldn't be any overhead compared to positional arguments once JIT'ed. In Ruby 2.7: * The caller needs to pass positional and keyword arguments separately, at least when calling a method accepting kwargs. But, if it calls a methods not accepting kwargs, then the "kwargs" (e.g. `foo(key: :value)`) should be treated just like a final Hash positional argument. * (If we had complete separation, then we could always pass positional and keyword arguments separately, so the caller could once again ignore the callee) How is the logic implemented in MRI for 2.7? Specializing the caller for a given callee is a well-known technique. However, it becomes more difficult if different methods are called from the same callsite (polymorphic call), especially if one accepts kwargs and another does not. In that case, I think we will see a performance cost to this approach, by having to pass arguments differently based on the method to be called. What about delegation using `ruby2_keywords`? Which checks does that add (compared to 2.6) in the merged approach with the Hash flag? -- https://bugs.ruby-lang.org/