From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx177.postini.com [74.125.245.177]) by kanga.kvack.org (Postfix) with SMTP id 0C6706B004D for ; Tue, 8 May 2012 05:16:01 -0400 (EDT) From: Subject: RE: [PATCH 3/3] vmevent: Implement special low-memory attribute 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: Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: penberg@kernel.org, kosaki.motohiro@gmail.com Cc: anton.vorontsov@linaro.org, minchan@kernel.org, john.stultz@linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org, patches@linaro.org, kernel-team@android.com > -----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); Joh= n ... > >> That comes from a real-world requirement. See Leonid's email on the to= pic: > >> > >> 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. >=20 > Leonid? The "usleep(timeout); read(vmevent_fd)" will eliminate opportunity to use v= mevent API for mobile devices. =20 Developers already have to use heartbeat primitives to align/sync timers an= d 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 d= ue to memory situation may change a lot in short time. Short depends from software stack but usually it below 1s. To have use-tim= e and wakeups on good level (below 50Hz by e.g. powertop) and allow cpu swi= tch off timers of such short period like 1s are not allowed. Leonid PS: Sorry, meetings prevent to do interesting things :( I am tracking conv= ersation with quite low understanding how it will be useful for practical n= eeds because user-space developers in 80% cases needs to track simply dirty= memory changes i.e. modified pages which cannot be dropped. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org