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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2BFD0C433E0 for ; Thu, 4 Jun 2020 01:38:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EDCAD20657 for ; Thu, 4 Jun 2020 01:38:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EDCAD20657 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7B3188000E; Wed, 3 Jun 2020 21:38:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 762958000C; Wed, 3 Jun 2020 21:38:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 62BA08000E; Wed, 3 Jun 2020 21:38:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0025.hostedemail.com [216.40.44.25]) by kanga.kvack.org (Postfix) with ESMTP id 4730E8000C for ; Wed, 3 Jun 2020 21:38:40 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 066487FD84 for ; Thu, 4 Jun 2020 01:38:40 +0000 (UTC) X-FDA: 76889820000.09.guide42_688527e2f0952 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id DF1C3180AD804 for ; Thu, 4 Jun 2020 01:38:39 +0000 (UTC) X-HE-Tag: guide42_688527e2f0952 X-Filterd-Recvd-Size: 2865 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Thu, 4 Jun 2020 01:38:38 +0000 (UTC) IronPort-SDR: 4noHoVevL7tVrP5i3TrcNHIJme5syPOJEGwG+lzpwNKE1gyun6qQWVxfNON0bfZK1t/cKExJh4 WTslRgsXaxCg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2020 18:38:36 -0700 IronPort-SDR: AMeEWEXdU0inFl0oDvKKYFvVG5qMv7/RoO6AJbLXkzSGLUn61i1MaJwznPHZtvjV2j5969ySAM bFeLKhv71VcQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,470,1583222400"; d="scan'208";a="269260744" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.107]) by orsmga003.jf.intel.com with ESMTP; 03 Jun 2020 18:38:33 -0700 Date: Thu, 4 Jun 2020 09:38:32 +0800 From: Feng Tang To: Andi Kleen 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: <20200604013832.GD89848@shbuild999.sh.intel.com> References: <1590714370-67182-1-git-send-email-feng.tang@intel.com> <1590714370-67182-3-git-send-email-feng.tang@intel.com> <20200603142853.GE621576@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200603142853.GE621576@tassilo.jf.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Rspamd-Queue-Id: DF1C3180AD804 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 03, 2020 at 07:28:53AM -0700, Andi Kleen wrote: > > 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. Agree. Maybe I should also put the time cost info into the code comments in case someone noticed the slowdown. Thanks, Feng > > -Andi