Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760041Ab2FEI0x (ORCPT ); Tue, 5 Jun 2012 04:26:53 -0400 Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:58415 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757973Ab2FEI0v (ORCPT ); Tue, 5 Jun 2012 04:26:51 -0400 X-AuditID: 9c93016f-b7c3cae000001954-2b-4fcdc2c9a838 Message-ID: <4FCDC2E1.4080004@kernel.org> Date: Tue, 05 Jun 2012 17:27:13 +0900 From: Minchan Kim User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel.mm,gmane.linux.kernel To: leonid.moiseichuk@nokia.com CC: penberg@kernel.org, cbouatmailru@gmail.com, kosaki.motohiro@gmail.com, 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 Subject: Re: [PATCH 0/5] Some vmevent fixes... References: <20120601122118.GA6128@lizard> <4FCC7592.9030403@kernel.org> <20120604113811.GA4291@lizard> <20120604121722.GA2768@barrios> <20120604133527.GA13650@lizard> <4FCDBC8E.1000705@kernel.org> <84FF21A720B0874AA94B46D76DB98269045EBBD8@008-AM1MPN1-003.mgdnok.nokia.com> In-Reply-To: <84FF21A720B0874AA94B46D76DB98269045EBBD8@008-AM1MPN1-003.mgdnok.nokia.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1881 Lines: 38 On 06/05/2012 05:16 PM, leonid.moiseichuk@nokia.com wrote: >> -----Original Message----- >> From: penberg@gmail.com [mailto:penberg@gmail.com] On Behalf Of ext >> Pekka Enberg >> Sent: 05 June, 2012 11:02 >> To: Minchan Kim > ... >>> Next concern is that periodic timer of implementation. >>> I think it would add direct hook in vmscan.c rather than peeking raw >>> vmstat periodically by timer so we can control more fine-grained way >> without unnecessary overhead. >> >> If the hooks are clean and it doesn't hurt the !CONFIG_VMEVENT case, I'm >> completely OK with that. > > On the previous iteration hooking vm was pointed as very bad idea, so in my version I installed shrinker to handle cases when we have memory pressure. > Using deferred timer with adequate timeout (0.250 ms or larger) fully suitable for userspace and produce adequate overhead > -> by nature such API should not be 100% accurate, anyhow applications cannot handle situation as good as kernel can provide, 0.5MB space accuracy, 100ms is maximum user-space require for 64-1024MB devices. > I didn't follow previous iteration you mentioned so I don't know the history. I think it's a not good idea if LMN(low memory notifier) is needed by only embedded world. Maybe in that case, we might control it enough by only vmstat events but now we know many folks want it so we are trying to make it general. IMHO, for meeting various requirement, vmstat raw event isn't enough so we need direct hook in vmscan and should abstract it to some levels. Of course, VM guys should maintain it to work best as VM algorithm are changing. -- Kind regards, Minchan Kim -- 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/