Date: Wed, 31 Mar 2010 17:14:08 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Tsuyoshi Ozawa <ozawa+bsd@t-oza.net> Cc: =?ISO-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no>, Roman Divacky <rdivacky@freebsd.org>, Julian Elischer <julian@elischer.org>, freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: Dynamic ticks in FreeBSD Message-ID: <4BB358B0.4090300@icyb.net.ua> In-Reply-To: <p2p411a180c1003310505qb6e274f2i7b39aa3dd7387d24@mail.gmail.com> References: <411a180c1003300537g2a1b4879u2d8d952ce9977cb5@mail.gmail.com> <411a180c1003300639l13d33451q305a61b2bcd6e3d5@mail.gmail.com> <20100330173504.GA70578@freebsd.org> <p2p411a180c1003310505qb6e274f2i7b39aa3dd7387d24@mail.gmail.com>
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on 31/03/2010 15:05 Tsuyoshi Ozawa said the following: > Thank you for replying ! > > The patch for FreeBSD 8.0 original source is here : > http://gist.github.com/350230 > If this patch cause collision, I'm going to throw patch between > FreeBSD 8.0 HEAD and my chage. (sorry for this, I cannot connect to > CVS repository now for network reason. It take a few days to connect > CVS repository.) Thank you for this interesting and useful work! I looked through the code and here is my understanding of how it works, it coincides with how you described it, but I'd like to state it in my own words :-) 1. Instead of firing clock (LAPIC timer) interrupt regularly with a frequency derived from HZ, the interrupt is scheduled to fire (in one-shot mode) at the time of the soonest scheduled callout. 2. The code also makes sure to run hard/stat/prof-clocks if time since last interrupt is greater than their respective periods in !dyntick mode. Thus, it appears that in dyntick mode hard/stat/prof-clocks would run irregularly. I couldn't find any code that makes sure that the rest of the system handles this properly. Perhaps I missed it, or is it still in progress/plans? Also, I am not sure if the code handles the case when a new 'soonest' callout is scheduled after we already decided when to fire the next LAPIC timer interrupt. Thank you very much again! Please keep up the good work :) -- Andriy Gapon
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