Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752269Ab2EHJQJ (ORCPT ); Tue, 8 May 2012 05:16:09 -0400 Received: from smtp.nokia.com ([147.243.128.26]:39905 "EHLO mgw-da02.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926Ab2EHJQH convert rfc822-to-8bit (ORCPT ); Tue, 8 May 2012 05:16:07 -0400 From: To: , CC: , , , , , , , Subject: RE: [PATCH 3/3] vmevent: Implement special low-memory attribute Thread-Topic: [PATCH 3/3] vmevent: Implement special low-memory attribute Thread-Index: AQHNJ54zt9884we850qVfkvWrpHZv5a463aAgAA1ewCABLBlgIAAE/cAgABAG4CAAHaTAIAAp8wAgAAGDoCAAANQAIAAFcOAgAAG5oCAAAPpAIAAA4SAgAAyfPA= Date: Tue, 8 May 2012 09:15:46 +0000 Message-ID: <84FF21A720B0874AA94B46D76DB98269045D63B3@008-AM1MPN1-003.mgdnok.nokia.com> References: <20120501132409.GA22894@lizard> <20120501132620.GC24226@lizard> <4FA35A85.4070804@kernel.org> <20120504073810.GA25175@lizard> <20120507121527.GA19526@lizard> <4FA82056.2070706@gmail.com> <4FA8D046.7000808@gmail.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.162.29.9] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-OriginalArrivalTime: 08 May 2012 09:15:47.0707 (UTC) FILETIME=[27A3C4B0:01CD2CFB] X-Nokia-AV: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1827 Lines: 30 > -----Original Message----- > From: penberg@gmail.com [mailto:penberg@gmail.com] On Behalf Of ext > Pekka Enberg > Sent: 08 May, 2012 11:03 > To: KOSAKI Motohiro > Cc: Anton Vorontsov; Minchan Kim; Moiseichuk Leonid (Nokia-MP/Espoo); John ... > >> That comes from a real-world requirement. See Leonid's email on the topic: > >> > >> https://lkml.org/lkml/2012/5/2/42 > > > > I know, many embedded guys prefer such timer interval. I also have an > > experience similar logic when I was TV box developer. but I must > > disagree. Someone hope timer housekeeping complexity into kernel. but > > I haven't seen any justification. > > Leonid? The "usleep(timeout); read(vmevent_fd)" will eliminate opportunity to use vmevent API for mobile devices. Developers already have to use heartbeat primitives to align/sync timers and update code which is not always simple to do. But the idea is to have user-space wakeup only if we have something change in memory numbers, thus aligned timers will not help much in vmevent case due to memory situation may change a lot in short time. Short depends from software stack but usually it below 1s. To have use-time and wakeups on good level (below 50Hz by e.g. powertop) and allow cpu switch off timers of such short period like 1s are not allowed. Leonid PS: Sorry, meetings prevent to do interesting things :( I am tracking conversation with quite low understanding how it will be useful for practical needs because user-space developers in 80% cases needs to track simply dirty memory changes i.e. modified pages which cannot be dropped. -- 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/