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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 3E063C76188 for ; Tue, 16 Jul 2019 11:04:35 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 10C36206C2 for ; Tue, 16 Jul 2019 11:04:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="GJPeSLgK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10C36206C2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=I6ZMK6n7LyERbYp24IicwVa/OVRDdyPi2bFR6cwNt2Q=; b=GJPeSLgK/FEGW7 t2minh1UGLsMiOSrMP89Q34DtV4pO7DGz3EDnIhQlZGmWZ38Tpsf++rAH9qLSGNUvNrlWhk7HthCW Ws8npJbc+f12s90T/rLjDt9H5CaOoidglnwpVZ2Xi1wexn9zK7AeU6i9b4/HrgrBtSOxKDVahOqa4 V2AdM51A06PlddTulhHmb59Q7blw+Iqb4ZJ+cWnRNkOgyr482Z3N01vvBjqB//qCf6E2M/fLmpBtR bW99xLDv6YaqEKH9iKZWkrpleeKWqyLaYFH5d87jZI9duN64zIu8BjJy4SpYgbUEzV++tjKtqgpyY sOj1HKheri/5Pmc0WShA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hnLG5-0004da-R6; Tue, 16 Jul 2019 11:04:33 +0000 Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hnLG1-0004dN-Ta; Tue, 16 Jul 2019 11:04:30 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9DEA0201D171F; Tue, 16 Jul 2019 13:04:27 +0200 (CEST) Date: Tue, 16 Jul 2019 13:04:27 +0200 From: Peter Zijlstra To: Waiman Long Subject: Re: [PATCH v3 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Message-ID: <20190716110427.GP3419@hirez.programming.kicks-ass.net> References: <20190715192536.104548-1-alex.kogan@oracle.com> <20190715192536.104548-4-alex.kogan@oracle.com> <77bba626-f3e6-45a8-aae8-43b945d0fab9@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <77bba626-f3e6-45a8-aae8-43b945d0fab9@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, guohanjun@huawei.com, arnd@arndb.de, dave.dice@oracle.com, jglauber@marvell.com, x86@kernel.org, will.deacon@arm.com, linux@armlinux.org.uk, linux-kernel@vger.kernel.org, rahul.x.yadav@oracle.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, Alex Kogan , steven.sistare@oracle.com, tglx@linutronix.de, daniel.m.jordan@oracle.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 15, 2019 at 05:30:01PM -0400, Waiman Long wrote: > On 7/15/19 3:25 PM, Alex Kogan wrote: > > /* > > - * On 64-bit architectures, the mcs_spinlock structure will be 16 bytes in > > - * size and four of them will fit nicely in one 64-byte cacheline. For > > - * pvqspinlock, however, we need more space for extra data. To accommodate > > - * that, we insert two more long words to pad it up to 32 bytes. IOW, only > > - * two of them can fit in a cacheline in this case. That is OK as it is rare > > - * to have more than 2 levels of slowpath nesting in actual use. We don't > > - * want to penalize pvqspinlocks to optimize for a rare case in native > > - * qspinlocks. > > + * On 64-bit architectures, the mcs_spinlock structure will be 20 bytes in > > + * size. For pvqspinlock or the NUMA-aware variant, however, we need more > > + * space for extra data. To accommodate that, we insert two more long words > > + * to pad it up to 36 bytes. > > */ > The 20 bytes figure is wrong. It is actually 24 bytes for 64-bit as the > mcs_spinlock structure is 8-byte aligned. For better cacheline > alignment, I will like to keep mcs_spinlock to 16 bytes as before. > Instead, you can use encode_tail() to store the CNA node pointer in > "locked". For instance, use (encode_tail() << 1) in locked to > distinguish it from the regular locked=1 value. Yes, please don't bloat this. I already don't like what Waiman did for the paravirt case, but this is horrible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel