Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754044Ab2KGApR (ORCPT ); Tue, 6 Nov 2012 19:45:17 -0500 Received: from smtp.getmail.no ([84.208.15.66]:60469 "EHLO smtp.getmail.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753527Ab2KGApQ (ORCPT ); Tue, 6 Nov 2012 19:45:16 -0500 MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes To: LKML Subject: Re: Help low-jitter man. References: <50992F56.3080209@paradoxuncreated.com> <50993696.8040006@paradoxuncreated.com> Date: Wed, 07 Nov 2012 01:45:13 +0100 From: Ove Karlsen Message-id: In-reply-to: <50993696.8040006@paradoxuncreated.com> User-Agent: Opera Mail/12.02 (Linux) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2815 Lines: 66 On Tue, 06 Nov 2012 17:11:02 +0100, Ove Karlsen wrote: > Den 06.11.2012 16:40, skrev Ove Karlsen: >> Heya, it`s me again. I am getting my low-jitter E5 computer, soon, and I >> have done all the tweaks I can think of with the kernel. >> >> I was wondering if anyone had anything to add, any good technical >> opinion on reducing jitter (for workstation desktop/OpenGL). >> >> I have a kernel with "low latency desktop" enabled. And edited >> Kconfig.hz to 90. >> idle=poll and tick_skew=1 in boot options. >> Compile a shaved local kernel by doing "make localmodconfig" from a full >> distro kernel. >> (Also turned of high_res_timers, to get 90hz) >> >> CFS granularity 1158500nS. (Current setting is a bit high) >> Reniced X to -20, to prevent X being a bottleneck. >> Remove 60hz limit in doom 3, to avoid timing jitter. >> http://paradoxuncreated.com/tmp/AutoExec.cfg >> >> Some nvidia-specific stuff on my blog aswell : >> http://paradoxuncreated.com/Blog/wordpress/?p=2268 >> >> A lot of people think SLAB has lower jitter than SLUB etc, aswell, and >> some tuning with regards to what kernel options execute the least code, >> least background activity can be done. Opinions? >> >> I use SLUB currently, and have turned off mem-compaction. >> And probably all kinds of debugging, counters and tracers. >> >> RCU boost to 99. >> >> I think I have collected most the relevant data for a low-jitter linux >> config. but in case there is additional information, I would love to >> hear it. >> >> Also ACPI on or off seems to be varying opions on. Some state ACPI >> removes SMI`s? I don`t know what is true here, and knowing that some >> recommend 10000hz timer for "low-jitter" (which is going the completely >> wrong way) I would like to hear your opinion on this aswell. >> >> Also approaching a transparent OS, with realtime-threads is interesting. >> Such as running maintask (optionally + depencies) as realtime. >> Unfortunately it doesn`t seem to work so well with standard FIFO. Do you >> think deadline could help this? Accurate 0.95ms of 1ms would be >> interesting to try. >> >> Also if anyone knows a linux-distro with the same philosophy throughout >> the OS, I would be interested to know about it. >> > > Also have anyone given any thoughts to vsynced HZ? And also even > possibly dividing subhz off that, or more hz counters if neccesary. Ok, I think after this, simple renicing seems to reduce significant amounts of jitter. So then the question becomes, how far can you take renice. Peace Be With you. -- 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/