Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759770Ab2FHDfZ (ORCPT ); Thu, 7 Jun 2012 23:35:25 -0400 Received: from mail-qc0-f174.google.com ([209.85.216.174]:56457 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753169Ab2FHDfY (ORCPT ); Thu, 7 Jun 2012 23:35:24 -0400 Message-ID: <4FD172F8.7050301@gmail.com> Date: Thu, 07 Jun 2012 23:35:20 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: leonid.moiseichuk@nokia.com CC: penberg@kernel.org, minchan@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; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1474 Lines: 27 (6/5/12 4:16 AM), 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 believe that's bad idea. In fact, An "adequate" timeout depend on hardware, not application performance tendency. Thus, applications can't know "adequate" value. -- 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/