From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86151C433DF for ; Wed, 3 Jun 2020 13:35:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6243420674 for ; Wed, 3 Jun 2020 13:35:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591191335; bh=xIJ78WqCPDXXk0402bFHxK/2TnjqYqbfayPj2IN8XTc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=jvPg32+vlsBtxigzZqJ+n1/aTXImNgVG3t8dANRneXxfJ9xd4/pYdmFYrj2wwmyPV I6h4SYLA4B9U/uUCL75a863EpNbSXr98j0LuyJ9J4M/ujGC9Mqtj00n2bfUdbOkpkI YNKdNvWS3eoSmNUUwlbRjncPpmz0ohWtUfUP4H+s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726066AbgFCNfe (ORCPT ); Wed, 3 Jun 2020 09:35:34 -0400 Received: from mail-ej1-f65.google.com ([209.85.218.65]:34557 "EHLO mail-ej1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725834AbgFCNfe (ORCPT ); Wed, 3 Jun 2020 09:35:34 -0400 Received: by mail-ej1-f65.google.com with SMTP id l27so2213538ejc.1 for ; Wed, 03 Jun 2020 06:35:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=HMfuPrTv7nZgMPcnR6scpe04ZPIW4XYf31Wlqr4SBCU=; b=bHliBKqW7Y6sT0/azf2UROQGwllxYWKNEoXDhMx1Q0MJ5tPEaJfu2sH+BPBSwYldxy A3HOLc1VEGCtQ6MPVJ1pNZ7uOj1QsTxEcwW0QwczMJ34C5z1aUnXZ0Uz+4wo+JFr9mgz rIr3AVPRXuJN15/53KHFpWon1D+ws89bFQviuWX+4eHk5WH2XCg7onmq0KC1sybo1H6d VMMp3b4m1gdjFckUUvkU6A7GT+IsPW4cFHVR3zm8PSc3IcK2VJWwC/JBlWyJzopYPg3h JToqQtzI9o0ZxL4CrPfKLCiJT72ui7wKf45WpXo+nl9Ai+fKYvI2jlkho90TI8f8m0LH 6ysQ== X-Gm-Message-State: AOAM53293DEMNDvYlAfjAiD6YRQMUXcW4W420IAnLYTkVyINON93XSvi 8NS7wmzAF3Aam9Nzni9X5Uc= X-Google-Smtp-Source: ABdhPJx/tNh+j12opk4X5dPeEPB24shY1lt2sstGdKjo8olNYMWFwR8nSVgzyf7La+mvmB2x+POkGw== X-Received: by 2002:a17:906:fb9b:: with SMTP id lr27mr2335640ejb.405.1591191330752; Wed, 03 Jun 2020 06:35:30 -0700 (PDT) Received: from localhost (ip-37-188-178-109.eurotel.cz. [37.188.178.109]) by smtp.gmail.com with ESMTPSA id z3sm1135456ejl.38.2020.06.03.06.35.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jun 2020 06:35:29 -0700 (PDT) Date: Wed, 3 Jun 2020 15:35:28 +0200 From: Michal Hocko To: Feng Tang Cc: Andrew Morton , Johannes Weiner , Matthew Wilcox , Mel Gorman , Kees Cook , Qian Cai , andi.kleen@intel.com, tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Haiyang Zhang Subject: Re: [PATCH v4 2/4] mm/util.c: make vm_memory_committed() more accurate Message-ID: <20200603133528.GJ7533@dhcp22.suse.cz> References: <1590714370-67182-1-git-send-email-feng.tang@intel.com> <1590714370-67182-3-git-send-email-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1590714370-67182-3-git-send-email-feng.tang@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 29-05-20 09:06:08, Feng Tang wrote: > percpu_counter_sum_positive() will provide more accurate info. > > As with percpu_counter_read_positive(), in worst case the deviation > could be 'batch * nr_cpus', which is totalram_pages/256 for now, > and will be more when the batch gets enlarged. > > Its time cost is about 800 nanoseconds on a 2C/4T platform and > 2~3 microseconds on a 2S/36C/72T server in normal case, and in > worst case where vm_committed_as's spinlock is under severe > contention, it costs 30~40 microseconds for the 2S/36C/72T sever, > which should be fine for its only two users: /proc/meminfo and > HyperV balloon driver's status trace per second. > > Signed-off-by: Feng Tang I cannot speak for HyperV part. Cc maintainers but this shouldn't be a problem for meminfo. Acked-by: Michal Hocko > --- > mm/util.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/util.c b/mm/util.c > index 9b3be03..3c7a08c 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -790,7 +790,7 @@ struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp; > */ > unsigned long vm_memory_committed(void) > { > - return percpu_counter_read_positive(&vm_committed_as); > + return percpu_counter_sum_positive(&vm_committed_as); > } > EXPORT_SYMBOL_GPL(vm_memory_committed); > > -- > 2.7.4 > -- Michal Hocko SUSE Labs