From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from albireo.enyo.de (albireo.enyo.de [37.24.231.21]) by sourceware.org (Postfix) with ESMTPS id 247A0385DC32; Mon, 4 May 2020 07:07:54 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 247A0385DC32 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=deneb.enyo.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=fw@deneb.enyo.de Received: from [172.17.203.2] (helo=deneb.enyo.de) by albireo.enyo.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) id 1jVVCi-0001E9-TB; Mon, 04 May 2020 07:07:52 +0000 Received: from fw by deneb.enyo.de with local (Exim 4.92) (envelope-from ) id 1jVVCi-0006vz-Pb; Mon, 04 May 2020 09:07:52 +0200 From: Florian Weimer To: Norbert Manthey Cc: libc-alpha@sourceware.org, Siddhesh Poyarekar Subject: Re: [[RFC][PATCH] v1 0/2] malloc/realloc with transparent huge page support References: <20200503220708.2048246-1-nmanthey@conp-solutions.com> <87ftcgz58n.fsf@mid.deneb.enyo.de> Date: Mon, 04 May 2020 09:07:52 +0200 In-Reply-To: (Norbert Manthey's message of "Mon, 4 May 2020 08:58:07 +0200") Message-ID: <87d07kw52v.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-9.7 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 May 2020 07:07:55 -0000 * Norbert Manthey: > I have seen [madvise] as the default for different Ubuntu versions > (16.04, 18.04 and 20.04), so I expect it to be around for at least the > next 5 years. Still, it is easier to change a run-time kernel setting than to upgrade glibc. >> In the paper, you say this: >> >> | Because there might be applications running on the host that would >> | suffer from larger pages, THP is usually disabled on physical >> | systems and it is not advised to set the value to always. >> >> However, the default value for Red Hat Enterprise Linux 7 is, in fact, >> "always", so it is puzzling why you see such a large benefit for >> long-running processes. > > All used test systems have not been using [always], but [madvise]. For > systems that already use [always], I expect the benefit to be much > smaller. With the 2M alignment, there should be less 4K pages required, > but we did not really measure the effect of only using the alignment. I suggest to repeat the experiment with "always". There is a reason why this setting exists. The results presented so far are incomplete. The paper doesn't provide details on the NUMA configuration of the test system, so one has to wonder if there are any surprises there as well.