From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout03.t-online.de (mailout03.t-online.de [194.25.134.81]) by sourceware.org (Postfix) with ESMTPS id E545D3858D33 for ; Sun, 15 Oct 2023 13:04:10 +0000 (GMT) ARC-Filter: OpenARC Filter v1.0.0 sourceware.org E545D3858D33 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=194.25.134.81 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1697375053; cv=none; b=Hw0ad7BMSLCBVseDH28jwAZo+F7HRFvx4WnvsRiL/S42JTHqgd6xCzf5fM5OvGj65LpadT7ogEnA5SD9XL1bR0Rg6X8nfhJX6Whz5gN/aNMz2KjqseNYDzoU8uxDh3poeJc3wWWWWK8zpLxvli9ZPQ/89LMoRAxjBxGFoMSlPDw= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1697375053; c=relaxed/simple; bh=PhbdCzcCXadGNvMjp11URvkgiUnSiAd9YV4POCHHKOM=; h=Subject:To:From:Message-ID:Date:MIME-Version; b=RWvkYEAlYimzG0k9epn6onymkZGvda0JZydberRTsaLoP3cccdOVWY4Amsj+DaHPfPSpZNBdvA/XSNoFKE1sFU30OetP9yKb56+xjoetLiQBQY6QtJcGkzLo7iHDeVQ5HwHvh6BhUjpRxzAfwm2QbYRND2H5WWGag6EPrXJiECk= ARC-Authentication-Results: i=1; server2.sourceware.org DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org E545D3858D33 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=t-online.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=t-online.de Received: from fwd87.aul.t-online.de (fwd87.aul.t-online.de [10.223.144.113]) by mailout03.t-online.de (Postfix) with SMTP id 9E18C3C3BA for ; Sun, 15 Oct 2023 15:04:07 +0200 (CEST) Received: from [192.168.2.101] ([79.230.173.210]) by fwd87.t-online.de with (TLSv1.3:TLS_AES_256_GCM_SHA384 encrypted) esmtp id 1qs0ms-2wBj160; Sun, 15 Oct 2023 15:04:06 +0200 Subject: Re: Run a Cygwin process with "higher" scheduler priority To: cygwin@cygwin.com References: <6652d1ac-6ed9-824c-1bca-28ac49d01db7@cs.umass.edu> From: Christian Franke Message-ID: Date: Sun, 15 Oct 2023 15:04:06 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 SeaMonkey/2.53.16 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TOI-EXPURGATEID: 150726::1697375046-FD3DFD6D-53B13B0D/0/0 CLEAN NORMAL X-TOI-MSGID: 7e1dc5cb-a80f-4692-a4c5-c5a303a402fe X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,BODY_8BITS,FREEMAIL_FROM,KAM_DMARC_STATUS,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Brian Inglis via Cygwin wrote: > On 2023-10-14 07:47, Eliot Moss via Cygwin wrote: >> On 10/14/2023 7:39 AM, Cedric Blancher via Cygwin wrote: >>> On Fri, 11 Aug 2023 at 19:14, Brian Inglis wrote: >>>> ... >>> >>>> ... >>>> $ cygcheck -p usr/bin/chrt >>>> Found 2 matches for usr/bin/chrt >>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info >>>> for util-linux >>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities >>>> $ cygcheck -p usr/bin/taskset >>>> Found 2 matches for usr/bin/taskset >>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info >>>> for util-linux >>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities >>>> so you may need to install util-linux (coreutils is already >>>> installed as a base >>>> package for Cygwin) then: >>>>          $ man nice renice taskset chrt >>> chrt does not work, the syscalls for realtime seem to be not >>> implemented. These are partly implemented, but sched_setscheduler() always fails with ENOSYS because scheduler policy (SCHED_*) cannot be changed on Windows. Changing priority only with sched_setparam() would work, but this is not used by chrt. >>>> You may need to run these from an elevated admin shell for other >>>> user ids, >>>> unowned processes, or higher (negative) priority. >>>> It has been years since I tried these so can no longer remember if -20 >>>> corresponds to Windows "RealTime" or if you need to use PowerShell >>>> to set that e.g. >>>>          $proc   = Get-Process -ProcessName "..." >>>>          $proc.PriorityClass     = "RealTime" >>>> and that needs to be done from an elevated admin (Power)Shell. >>>> Of course, never set that on any system except on a very idle, very >>>> I/O bound, >>>> well tested process, such as ntpd, that needs stably fast interrupt >>>> service and >>>> non-preemptible cpu access for ms every few seconds, preferably on >>>> a single or >>>> few cpus to which affinity is set. >>> Is there anything in /proc which can tell me the current *Windows* >>> scheduler priority level? Or a command line tool? >> I recall getting taskset going in util-linux a while back, but I don't >> recall working on priority related things.  You could look into the >> cygwin source code to see how Windows priorities relate to the priority >> values in Cygwin.  Then you may be able just to use /proc/[pid]/stat >> read out what you want. > > ISTR testing nice/renice, and found it was a simple priority mapping > to/from Unix to Windows Idle to RealTime (at the time, process > Affinity was not supported, so went with a PowerShell startup script > instead); see: > > https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l107 > > > https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l234 > > > https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l277 > The above maps priorities for sched_*() API. The mapping for nice() and get/setpriority() is done here: https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/miscfuncs.cc;h=767384f#l110 > They are documented in proc(5) /proc/PID/stat fields 18 priority and > 19 nice typically 20 and 0, as shown by `top` PR and NI, shown by > `procps -l` as 80 and 0, and not shown by Cygwin `ps`. On Cygwin, field 18 is always equal to (field_19 + 20). The priority value returned by sched_getparam() is different and could be shown with 'chrt -p PID'. The output from the command 'nice' without parameter may differ from /proc/PID/stat field 19 because the latter always reinterprets the current Windows prio class. This script prints a table of 'nice' outputs, /proc/PID/stat fields 19 and 18, result of sched_getparam() and corresponding Windows prio class for different 'nice -n ...' commands: #!/bin/bash echo "COMMAND    : NICE  STAT STPRI RTPRI  WINPRI" for i in {-21..20}; do   nice -n $i sh -e -c '     n=$(nice)     s=$(cut -d" " -f19 /proc/$$/stat)     p=$(cut -d" " -f18 /proc/$$/stat)     r=$(LC_MESSAGES=C chrt -p $$ | sed -n "s,^.*priority: ,,p")     case $r in       3)  c="IDLE_PRIORITY_CLASS" ;;       9)  c="BELOW_NORMAL_PRIORITY_CLASS" ;;       15) c="NORMAL_PRIORITY_CLASS" ;;       21) c="ABOVE_NORMAL_PRIORITY_CLASS" ;;       27) c="HIGH_PRIORITY_CLASS" ;;       32) c="REALTIME_PRIORITY_CLASS" ;;       *)  c="?" ;;     esac     printf "nice -n %3d:%5d %5d %5d %5d  %s\\n" \            "'$i'" "$n" "$s" "$p" "$r" "$c"   ' done -- Regards, Christian