From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx149.postini.com [74.125.245.149]) by kanga.kvack.org (Postfix) with SMTP id 8A7396B006E for ; Thu, 7 Jun 2012 23:35:24 -0400 (EDT) Received: by qcsd16 with SMTP id d16so821874qcs.14 for ; Thu, 07 Jun 2012 20:35:23 -0700 (PDT) Message-ID: <4FD172F8.7050301@gmail.com> Date: Thu, 07 Jun 2012 23:35:20 -0400 From: KOSAKI Motohiro MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: 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 (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, 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/ . Don't email: email@kvack.org