From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759664Ab2FHHD1 (ORCPT ); Fri, 8 Jun 2012 03:03:27 -0400 Received: from mail-yx0-f174.google.com ([209.85.213.174]:33150 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756309Ab2FHHDZ (ORCPT ); Fri, 8 Jun 2012 03:03:25 -0400 MIME-Version: 1.0 In-Reply-To: <20120608065828.GA1515@lizard> References: <20120601122118.GA6128@lizard> <1338553446-22292-2-git-send-email-anton.vorontsov@linaro.org> <4FD170AA.10705@gmail.com> <20120608065828.GA1515@lizard> Date: Fri, 8 Jun 2012 10:03:24 +0300 X-Google-Sender-Auth: khl-mFeWwLuDLLZ1tw9mBRO3z8k Message-ID: Subject: Re: [PATCH 2/5] vmevent: Convert from deferred timer to deferred work From: Pekka Enberg To: Anton Vorontsov Cc: KOSAKI Motohiro , Leonid Moiseichuk , Bartlomiej Zolnierkiewicz , John Stultz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org, patches@linaro.org, kernel-team@android.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 8, 2012 at 9:58 AM, Anton Vorontsov wrote: > If you're saying that we should set up a timer in the userland and > constantly read /proc/vmstat, then we will cause CPU wake up > every 100ms, which is not acceptable. Well, we can try to introduce > deferrable timers for the userspace. But then it would still add > a lot more overhead for our task, as this solution adds other two > context switches to read and parse /proc/vmstat. I guess this is > not a show-stopper though, so we can discuss this. > > Leonid, Pekka, what do you think about the idea? That's exactly the kind of half-assed ABI that lead to people inventing out-of-tree lowmem notifiers in the first place. I'd be more interested to know what people think of Minchan's that gets rid of vmstat sampling.