Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267381AbUJLBGp (ORCPT ); Mon, 11 Oct 2004 21:06:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269390AbUJLBFQ (ORCPT ); Mon, 11 Oct 2004 21:05:16 -0400 Received: from rwcrmhc11.comcast.net ([204.127.198.35]:46560 "EHLO rwcrmhc11.comcast.net") by vger.kernel.org with ESMTP id S266892AbUJLBDe (ORCPT ); Mon, 11 Oct 2004 21:03:34 -0400 Subject: Re: Difference in priority From: Albert Cahalan To: linux-kernel mailing list Cc: kernel@kolivas.org, ankitjain1580@yahoo.com, mingo@elte.hu, rml@tech9.net Content-Type: text/plain Organization: Message-Id: <1097542651.2666.7860.camel@cube> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.4 Date: 11 Oct 2004 20:57:31 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2890 Lines: 68 Con Kolivas writes: > Ankit Jain wrote: >> if somebody knows the difference b/w /PRI of both >> these commands because both give different results >> >> ps -Al >> & top >> >> as per priority rule we can set priority upto 0-99 >> but top never shows this high priority > > Priority values 0-99 are real time ones and 100-139 are normal > scheduling ones. RT scheduling does not change dynamic priority while > running wheras normal scheduling does (between 100-139). top shows the > value of the current dynamic priority in the PRI column as the current > dynamic priority-100. If you have a real time task in top it shows as a > -ve value. ps -Al seems to show the current dynamic priority+60. What would you like to see? There are numerous competing ideas of reality. There's also the matter of history and standards. I'd gladly "fix" ps, if people could agree on what "fix" would mean. Various desirable but conflicting traits include: a. for normal idle processes, PRI matches NI b. for RT processes, PRI matches RT priority c. for RT processes, PRI is negative of RT priority d. PRI is the unmodified value seen in /proc e. PRI is never negative f. low PRI is low priority (SysV "pri" keyword) g. low PRI is high priority (UNIX "PRI", SysV "opri") h. PRI matches some kernel-internal value i. PRI is in the range -99 to 999 (not too wide) I had originally tried to match up with Solaris and a few other systems, but that's looking hopeless. I intend to change to something sane, perhaps even making the PRI of "-o pri" be the same as that of "-l". Currently I don't even try to document PRI. It is good to keep the value narrow. I really wish we didn't have so many RT levels; POSIX only requires that there be 32. A simple 0..99 value would be great. Here is what I have in my current code, with the headers edited so they won't be confusing. Note that the left two versions ("aaa" and "bbb") are similar to the traditional SysV "pri", but the new POSIX and UNIX standard makes them unsuitable for use as the "PRI" displayed by "ps -l". It is common to generate the "PRI" of "ps -l" via an "opri" keyword. $ LD_LIBRARY_PATH=../../proc ../../ps/ps -t pts/8 --sort=-priority -o stat,pri,pri_api,rtprio,pri_bar,priority,pri_baz,opri,pri_foo,ni,cls,sched,comm STAT aaa bbb RTPRIO ccc ddd eee fff ggg NI CLS SCH COMMAND SN 0 -40 - 40 39 139 99 19 19 TS 0 setpriority19 Ss+ 23 -17 - 17 16 116 76 -4 0 TS 0 bash S< 39 -1 - 1 0 100 60 -20 -20 TS 0 setpriority-20 S 41 1 1 -1 -2 98 58 -22 - RR 2 min_rr S 139 99 99 -99 -100 0 -40 -120 - FF 1 max_fifo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/