From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750931AbWG3BXJ (ORCPT ); Sat, 29 Jul 2006 21:23:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750942AbWG3BXJ (ORCPT ); Sat, 29 Jul 2006 21:23:09 -0400 Received: from rwcrmhc11.comcast.net ([216.148.227.151]:19613 "EHLO rwcrmhc11.comcast.net") by vger.kernel.org with ESMTP id S1750931AbWG3BXI (ORCPT ); Sat, 29 Jul 2006 21:23:08 -0400 Subject: Re: itimer again (Re: [PATCH] RTC: Add mmap method to rtc character driver) From: Nicholas Miell To: Bill Huey Cc: Edgar Toernig , Neil Horman , Jim Gettys , "H. Peter Anvin" , Dave Airlie , Segher Boessenkool , linux-kernel@vger.kernel.org, a.zummo@towertech.it, jg@freedesktop.org, Keith Packard , Ingo Molnar , Steven Rostedt In-Reply-To: <20060730010020.GA23288@gnuppy.monkey.org> References: <44C6875F.4090300@zytor.com> <1153862087.1230.38.camel@localhost.localdomain> <44C68AA8.6080702@zytor.com> <1153863542.1230.41.camel@localhost.localdomain> <20060729042820.GA16133@gnuppy.monkey.org> <20060729125427.GA6669@localhost.localdomain> <20060729204107.GA20890@gnuppy.monkey.org> <20060729234948.0768dbf4.froese@gmx.de> <20060729225138.GA22390@gnuppy.monkey.org> <1154216151.2467.5.camel@entropy> <20060730010020.GA23288@gnuppy.monkey.org> Content-Type: text/plain Date: Sat, 29 Jul 2006 18:22:59 -0700 Message-Id: <1154222579.2467.12.camel@entropy> Mime-Version: 1.0 X-Mailer: Evolution 2.6.2 (2.6.2-1.fc5.5.0.njm.1) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2006-07-29 at 18:00 -0700, Bill Huey wrote: > On Sat, Jul 29, 2006 at 04:35:51PM -0700, Nicholas Miell wrote: > > On Sat, 2006-07-29 at 15:51 -0700, Bill Huey wrote: > > > [CCing Steve and Ingo on this thread] > > > > > > It's a different topic than what Keith needs, but this is useful for another > > > set of purposes. It's something that's really useful in the RT patch since > > > there isn't a decent API to get at high resolution timers in userspace. What > > > you've written is something that I articulated to Steve Rostedt over a dinner > > > at OLS and is badly needed in the -rt patches IMO. I suggest targeting that > > > for some kind of inclusion to Ingo Molnar's patchset. > > > > > > > Do you mind summarizing what's wrong with the existing interfaces for > > those of us who didn't have the opportunity to join you for dinner at > > OLS? > > Think edge triggered verse level triggered. Event interfaces in the Linux > kernel are sort of just that, edge triggered events. What RT folks generally > want is control over scheduling policies over a particular time period in > relation to a scheduling policy. A general kernel event interface isn't ^ Did you mean to say timer here? > going to cut it for those purpose and wasn't design to deal with those cases > in the first place. So you're asking for an automatic (perhaps temporary) change in scheduling policy when a particular timer expires (or perhaps on occurrence of other types of events)? I think Windows automatically boosts the priority of a thread when it delivers an I/O completion notification, and I'm pretty sure that Microsoft has a patent related to that. -- Nicholas Miell