From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on starla X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 Received: from nue.mailmanlists.eu (nue.mailmanlists.eu [94.130.110.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 26E5D1F4C4 for ; Mon, 4 Nov 2024 04:25:28 +0000 (UTC) Authentication-Results: dcvr.yhbt.net; dkim=pass (1024-bit key; unprotected) header.d=ml.ruby-lang.org header.i=@ml.ruby-lang.org header.a=rsa-sha256 header.s=mail header.b=N74ysNCF; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ruby-lang.org header.i=@ruby-lang.org header.a=rsa-sha256 header.s=s1 header.b=iyJfnpWV; dkim-atps=neutral DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ml.ruby-lang.org; s=mail; t=1730694295; bh=Z60a/M7yVeIjH0XOudfJCUgdk+8rU9VVHEFy5S1xwv8=; h=Date:References:To:Reply-To:Subject:List-Id:List-Archive: List-Help:List-Owner:List-Post:List-Subscribe:List-Unsubscribe: From:Cc:From; b=N74ysNCFrUzYBJ2vX7OLs+Ej9oUd5zOtBzFhxMM9K5wMQFYZu0j6zNVuZihAuxAEd 6JgqkNt4zF7JCtVcBZZCA+rOEaAMWCnXfVGQ2SAWdzwMgA02UQeGoluYJc6OIG3qzl 2ylxM1siJkxkLygisc+0thWWfu17UusIubo+5Uuo= Received: from nue.mailmanlists.eu (localhost [IPv6:::1]) by nue.mailmanlists.eu (Postfix) with ESMTP id 09B6544B16 for ; Mon, 4 Nov 2024 04:24:55 +0000 (UTC) Authentication-Results: nue.mailmanlists.eu; dkim=pass (2048-bit key; unprotected) header.d=ruby-lang.org header.i=@ruby-lang.org header.a=rsa-sha256 header.s=s1 header.b=iyJfnpWV; dkim-atps=neutral Received: from s.wrqvwxzv.outbound-mail.sendgrid.net (s.wrqvwxzv.outbound-mail.sendgrid.net [149.72.154.232]) by nue.mailmanlists.eu (Postfix) with ESMTPS id BC90F44522 for ; Mon, 4 Nov 2024 04:24:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ruby-lang.org; h=from:references:subject:mime-version:content-type: content-transfer-encoding:list-id:to:cc:content-type:from:subject:to; s=s1; bh=fitRLeEK3/sCselmVy/cyGtlhpDvuuByBV0CL6Kliw0=; b=iyJfnpWVqQbnu9rtcm1aqmQLNKIjFqUtQ2WfyufwhHpEoYd0Sg1h4xTurjfby/PhnQRT daJabsY1KuIqYXGHaScDPu9S3ZcqPZgnyFkH5g/v5tJrPiA8Y4z4XO42wjMOPOdxVjZRTX tUtx4lYJ9aBMzUtBZGomU3fmUa6kjPlDJaK5ljodRleu3VecntExdNwm2oPuZZOu3uNSph T/3SFtW1T3v8Q7QX4/LlpUOiV5WN1WEZGFFwr1PRVqnQ1MXsc5pg3b/fweFPpqZeYyQ6jC RUbMMwyw5sCSDt+iVVOxf/Se7mbcGcMrYOzmSKOEK+dmXyhBosTq+obsL4Gaj9hA== Received: by recvd-55fc7fd858-8mxwb with SMTP id recvd-55fc7fd858-8mxwb-1-67284C8A-1 2024-11-04 04:24:42.030181491 +0000 UTC m=+4530457.869815424 Received: from herokuapp.com (unknown) by geopod-ismtpd-10 (SG) with ESMTP id pLvoPpUGS6q9XgoiCt8LgQ for ; Mon, 04 Nov 2024 04:24:41.955 +0000 (UTC) Date: Mon, 04 Nov 2024 04:24:42 +0000 (UTC) Message-ID: References: Mime-Version: 1.0 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Feature X-Redmine-Issue-Id: 20861 X-Redmine-Issue-Author: tenderlovemaking X-Redmine-Issue-Priority: Normal X-Redmine-Sender: jhawthorn 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-Redmine-MailingListIntegration-Message-Ids: 96362 X-SG-EID: =?us-ascii?Q?u001=2EPbok3+7FQfebysnQr5TCCxGBI4YRNbbNoeLobvdWjgSQ5tpG6ZHb7cfml?= =?us-ascii?Q?cLpQRmscQ7YbcwEtJUBy=2Fno4fwnO2ualh0JafGy?= =?us-ascii?Q?DtBs5BQCLangudKJZ=2Fzm7CMtxKuL0XLPKhsDeBo?= =?us-ascii?Q?OcG4l9FQF2gx52MbW1B=2Fvthhr6auBt5LVg2Z34E?= =?us-ascii?Q?KK5v49yyedV987+pbEc+BQmqZnnax1DUrZopdt3?= =?us-ascii?Q?OI6isIpAfu9wmJxPUpaM0MhCnb67J06aum6Rp0i?= =?us-ascii?Q?ZOlvlxDa5K9uRLW1jGo1jILNDA=3D=3D?= To: ruby-core@ml.ruby-lang.org X-Entity-ID: u001.I8uzylDtAfgbeCOeLBYDww== Message-ID-Hash: DSCRICGFKMMG3EV6WF3LQSHZ7POAUWRW X-Message-ID-Hash: DSCRICGFKMMG3EV6WF3LQSHZ7POAUWRW X-MailFrom: bounces+313651-b711-ruby-core=ml.ruby-lang.org@em5188.ruby-lang.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.9 Precedence: list Reply-To: Ruby developers Subject: [ruby-core:119697] [Ruby master Feature#20861] Add an environment variable for tuning the default thread quantum List-Id: Ruby developers Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: "jhawthorn (John Hawthorn) via ruby-core" Cc: "jhawthorn (John Hawthorn)" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Issue #20861 has been updated by jhawthorn (John Hawthorn). I don't think we should expose the quantum per-thread inside Ruby. I worry it will prevent future improvements. The fact that Thread scheduling and priorities are currently done by giving a shorter/longer quantum is an implementation detail that could (and I'd like to) change. Thread `priority` is good *because* it is more abstract, which gives flexibility on implementation. Similarly I don't love `Thread.default_quantum=` as it's implementation specific - I wouldn't expect it to make sense for JRuby/TruffleRuby for example, and it's possible CRuby could have a different implementation in the future. Though I don't feel as strongly. I think an environment variable is best as it's very similar to how we allow tuning the garbage collector via environment variables. In the future if end up being able to remove this, that's much easier/safer with an environment variable. ---------------------------------------- Feature #20861: Add an environment variable for tuning the default thread quantum https://bugs.ruby-lang.org/issues/20861#change-110357 * Author: tenderlovemaking (Aaron Patterson) * Status: Open ---------------------------------------- The default thread quantum is currently [hard coded at 100ms](https://github.com/ruby/ruby/blob/c7708d22c33040a74ea7ac683bf7407d3759edfe/thread_pthread.c#L323). This can impact multithreaded systems that are trying to process Ruby level CPU bound work at the same time as IO work. I would like to add an environment variable `RUBY_THREAD_DEFAULT_QUANTUM_MS` that allows users to specify the default thread quantum (in milliseconds) via an environment variable. It defaults to our current default of 100ms. I've submitted the patch [here](https://github.com/ruby/ruby/pull/11981). Here is a Ruby program to demonstrate the problem: ```ruby def measure x = Process.clock_gettime(Process::CLOCK_MONOTONIC) yield Process.clock_gettime(Process::CLOCK_MONOTONIC) - x end def fib(n) if n < 2 n else fib(n-2) + fib(n-1) end end # find fib that takes ~500ms fib_i = 50.times.find { |i| measure { fib(i) } >= 0.05 } sleep_i = measure { fib(fib_i) } threads = [ Thread.new { 100.times { sleep(sleep_i) # sometimes stalled waiting for fib's quantum to finish } puts "done 1" }, Thread.new { 100.times { fib(fib_i) }; puts "done 2" }, ] # We expect the total time to be about 100 * sleep_i (~5 seconds) because # theoretically the sleep thread could be done nearly completely in parallel to # the fib thread. # # But because the `sleep` thread is iterating over the sleep call, it must wait # for the `fib` thread to complete its quantum, before it can start the next iteration. # # This means each sleep iteration could take up to `sleep_i + 100ms` # # We're calling that stalled time "waste" total = measure { threads.each(&:join) } waste = total - (sleep_i * 100) p TOTAL: total, WASTE: waste ``` The program has two threads. One thread is using CPU time by computing `fib` in a loop. The other thread is simulating IO time by calling `sleep` in a loop. When the `sleep` call completes, it can stall, waiting for the quantum in the fib thread to expire. That means that each iteration on sleep can actually take `sleep time + thread quantum`, or in this case ~600ms when we expected it to only take ~500ms. Ideally, the above program would take `500ms * 100` since all `sleep` calls should be able to execute in parallel with the `fib` calls. Of course this isn't true because the sleep thread must acquire the GVL before it can continue the next iteration, so there will always be _some_ overhead. This feature is for allowing people to tune that overhead. If we run this program with the default quantum the output looks like this: ``` $ ./miniruby -v fibtest.rb ruby 3.4.0dev (2024-11-01T14:49:50Z quantum-computing c7708d22c3) +PRISM [arm64-darwin24] done 2 done 1 {TOTAL: 12.672821999993175, WASTE: 4.960721996147186} ``` The output shows that our program spent about 5 seconds stalled, waiting to acquire the GVL. With this patch we can lower the default quantum, and the output is like this: ``` $ RUBY_THREAD_DEFAULT_QUANTUM_MS=10 ./miniruby -v fibtest.rb ruby 3.4.0dev (2024-11-01T22:06:35Z quantum-computing 087500643d) +PRISM [arm64-darwin24] done 2 done 1 {TOTAL: 8.898526000091806, WASTE: 1.4168260043952614} ``` Specifying the ENV to change the quantum to 10ms lowered our waste in the program to ~1.4 seconds. It's common for web applications to do mixed CPU and IO bound tasks in threads (see the Puma webserver), so it would be great if there was a way to customize the thread quantum depending on your application's workload. -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/