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=0.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_BL_SPAMCOP_NET,SPF_HELO_PASS, SPF_PASS autolearn=no 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 01AF11F4C1 for ; Thu, 14 Nov 2024 18:59:16 +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=mmDIgLq0; 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=HZKmSkHN; dkim-atps=neutral DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ml.ruby-lang.org; s=mail; t=1731610753; bh=NmID8IBjdaVesD8j3f03l5bRqB8MuwBwDG4NyW0naTc=; 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=mmDIgLq023rqVgPW0m35+XHTHCpqfFjFJA+lSD7CuQEs6qU5w78wuNCPqiDnwmdOa MqifHp5Kbw8v8KiiL883iVQsSfSWQocEA+3szp1YO1hheD1l/9ym82MVe7CAnEwvyl axmrHEfINcwYzozYlmaYsKn+JSJhrCpQFfB+ODLc= Received: from nue.mailmanlists.eu (localhost [IPv6:::1]) by nue.mailmanlists.eu (Postfix) with ESMTP id EE8EC44B8A for ; Thu, 14 Nov 2024 18:59:13 +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=HZKmSkHN; dkim-atps=neutral Received: from s.wrqvtvvn.outbound-mail.sendgrid.net (s.wrqvtvvn.outbound-mail.sendgrid.net [149.72.120.130]) by nue.mailmanlists.eu (Postfix) with ESMTPS id E07F844B44 for ; Thu, 14 Nov 2024 18:59:01 +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=NeIv43Z7ddSw2eH6+3sGlFIbi1AIWH57IYnU2/tsGzk=; b=HZKmSkHN5SkSQ7bJ4XTBj8YRMgGzPtL7Nq4pAn22+Ke4Z/Avev/tqiUCazhhks4nkKay W0U+0ceoHq/KaZRfs31c2YxghohCZumU664KOzipaDL3Xcnlnck+d1TMVF86GPGTBhBuL4 TIJW9vUV5UKUNa0xe4xCXpQ3Z2q8qj68QEVjP8E4n9wNTFHXv9P4JCe2vH8vm6Qo1EtsB6 b7E/YlmejdFSU4IVxmXXR44Xye/BaslqU1FKp722y0kQhDOohQAYJG5vpQpiuNXusF5RYQ Rrk29U6UFcattR4m8NgkpPgY4aCSgIPAU0pdUfQaUtrKNKE6TJ7YFMJpTiWpukUA== Received: by recvd-5577bcb48c-jbz28 with SMTP id recvd-5577bcb48c-jbz28-1-67364873-2F 2024-11-14 18:58:59.731964877 +0000 UTC m=+5446922.369362306 Received: from herokuapp.com (unknown) by geopod-ismtpd-32 (SG) with ESMTP id Xt3TUIy5QpaTGfPgEus6yg for ; Thu, 14 Nov 2024 18:58:59.686 +0000 (UTC) Date: Thu, 14 Nov 2024 18:58:59 +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: ivoanjo 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: 96606 X-SG-EID: =?us-ascii?Q?u001=2E6H93DVRiTiKc3wKayPWzh2RPR1DtIsXolb0VJaA3YPKvN=2FiUA=2FcDux7sI?= =?us-ascii?Q?AhPFlmPiB60E+4qdJR4WHqjbn+t0GQnkwSg0gIF?= =?us-ascii?Q?XzSBpBOpNu4lJr4Lq7oyLPaUe02JkImg11cG4gF?= =?us-ascii?Q?2tDCWTzGpXdliD7rFu2ABkLOpXASOfN9cHH=2F=2FxN?= =?us-ascii?Q?TWJ2JZGQeFw+tRZ=2FSChKTOUyseKoFmeLc5TGS9r?= =?us-ascii?Q?NwRfaOWar7t4++=2FzE9sqL=2FTtqjLXjmH3+WrLDUh?= =?us-ascii?Q?xQmd?= To: ruby-core@ml.ruby-lang.org X-Entity-ID: u001.I8uzylDtAfgbeCOeLBYDww== Message-ID-Hash: GNKF4L33LE2VWQ5EHHGKUDWZRMCSJSY3 X-Message-ID-Hash: GNKF4L33LE2VWQ5EHHGKUDWZRMCSJSY3 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:119935] [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: "ivoanjo (Ivo Anjo) via ruby-core" Cc: "ivoanjo (Ivo Anjo)" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Issue #20861 has been updated by ivoanjo (Ivo Anjo). Out of curiosity, Python has a way of setting the GIL switching interval too: https://docs.python.org/3.6/library/sys.html#sys.setswitchinterval . Default interval seems to be 5ms (https://github.com/python/cpython/blob/47cbf038850852cdcbe7a404ed7c64542340d58a/Python/ceval_gil.c#L152). ---------------------------------------- Feature #20861: Add an environment variable for tuning the default thread quantum https://bugs.ruby-lang.org/issues/20861#change-110656 * 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/