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_PASS,URIBL_BLOCKED autolearn=ham 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 2C6EBC43A1D for ; Thu, 12 Jul 2018 15:16:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7AA021471 for ; Thu, 12 Jul 2018 15:16:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D7AA021471 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732636AbeGLP0R (ORCPT ); Thu, 12 Jul 2018 11:26:17 -0400 Received: from 9.mo179.mail-out.ovh.net ([46.105.76.148]:39325 "EHLO 9.mo179.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732491AbeGLP0R (ORCPT ); Thu, 12 Jul 2018 11:26:17 -0400 X-Greylist: delayed 603 seconds by postgrey-1.27 at vger.kernel.org; Thu, 12 Jul 2018 11:26:16 EDT Received: from player756.ha.ovh.net (unknown [10.109.108.62]) by mo179.mail-out.ovh.net (Postfix) with ESMTP id 2CE33D805D for ; Thu, 12 Jul 2018 16:59:27 +0200 (CEST) Received: from bahia.lan (lns-bzn-46-82-253-208-248.adsl.proxad.net [82.253.208.248]) (Authenticated sender: groug@kaod.org) by player756.ha.ovh.net (Postfix) with ESMTPSA id CC7281200C3; Thu, 12 Jul 2018 16:59:15 +0200 (CEST) Date: Thu, 12 Jul 2018 16:59:14 +0200 From: Greg Kurz To: Dominique Martinet Cc: Matthew Wilcox , Latchesar Ionkov , Eric Van Hensbergen , linux-kernel@vger.kernel.org, Ron Minnich , linux-fsdevel@vger.kernel.org, v9fs-developer@lists.sourceforge.net Subject: Re: [V9fs-developer] [PATCH v2 4/6] 9p: Embed wait_queue_head into p9_req_t Message-ID: <20180712165914.7d1f949f@bahia.lan> In-Reply-To: <20180712144012.GA21574@nautica> References: <20180711210225.19730-1-willy@infradead.org> <20180711210225.19730-5-willy@infradead.org> <20180712163649.36057b6e@bahia.lan> <20180712144012.GA21574@nautica> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Ovh-Tracer-Id: 7840485479542331648 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedtiedrgeekgdekfecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 12 Jul 2018 16:40:12 +0200 Dominique Martinet wrote: > Greg Kurz wrote on Thu, Jul 12, 2018: > > This is true when all tags have been used at least once. But the current code > > lazily allocates the wait_queue_head_t, ie, only when a tag is used for the > > first time. Your patch causes a full row of wait_quest_head_t to be pre-allocated. > > > > ie, P9_ROW_MAXTAG * 24 = 255 * 24 = 6120 > > > > instead of (P9_ROW_MAXTAG * 8) + 24 = 255 * 8 + 24 = 2064 > > > > This is nearly a page of allocated memory that might be never used. > > > > Not sure if this is a problem though... > > I thought the exact same, but the next patch in the serie removes that > array and allocates even more lazily with a slab, so this was a > no-brainer :) > Ah ? I haven't started looking at that *big* other patch yet... :)