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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 15E0FC433DF for ; Wed, 3 Jun 2020 14:28:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E170320679 for ; Wed, 3 Jun 2020 14:28:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725961AbgFCO2z (ORCPT ); Wed, 3 Jun 2020 10:28:55 -0400 Received: from mga12.intel.com ([192.55.52.136]:53454 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725854AbgFCO2y (ORCPT ); Wed, 3 Jun 2020 10:28:54 -0400 IronPort-SDR: WV0zH0s8XSv8BRdyEGxIDsROb4Ce0WdPVLsYjxIA2Vs7lP9WnJJcsAgRXJrk8h+2QQcvgjFjhW YqY8fwoDVapw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2020 07:28:53 -0700 IronPort-SDR: XXUouqSJAn1VhHZCiNgfISHb83SMuN06jgxmcHhs3xupN+cDr+gpJegoaUAfhAJZO4c5N3xx7I r3jZCOk7K+Vg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,467,1583222400"; d="scan'208";a="269091278" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.21]) by orsmga003.jf.intel.com with ESMTP; 03 Jun 2020 07:28:53 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id 8CBF330166D; Wed, 3 Jun 2020 07:28:53 -0700 (PDT) Date: Wed, 3 Jun 2020 07:28:53 -0700 From: Andi Kleen To: Feng Tang Cc: Andrew Morton , Michal Hocko , Johannes Weiner , Matthew Wilcox , Mel Gorman , Kees Cook , Qian Cai , tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/4] mm/util.c: make vm_memory_committed() more accurate Message-ID: <20200603142853.GE621576@tassilo.jf.intel.com> 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 > 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, This will be likely 40-80us on larger systems, although the overhead is often non linear so it might get worse. > which should be fine for its only two users: /proc/meminfo and > HyperV balloon driver's status trace per second. There are some setups who do frequent sampling of /proc/meminfo in the background. Increased overhead could be a problem for them. But not proposing a change now. If someone complains have to revisit I guess, perhaps adding a rate limit of some sort. -Andi