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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 7BF8BC433E2 for ; Thu, 16 Jul 2020 10:22:40 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 4394F207F9 for ; Thu, 16 Jul 2020 10:22:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="O7qT433B" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4394F207F9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 000EC8A5BF; Thu, 16 Jul 2020 10:22:39 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CCzOXV7ME2yH; Thu, 16 Jul 2020 10:22:39 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 84A4C8A5BE; Thu, 16 Jul 2020 10:22:39 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6B089C07FF; Thu, 16 Jul 2020 10:22:39 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id BD29BC0733 for ; Thu, 16 Jul 2020 10:22:38 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id B4B8E8AFEF for ; Thu, 16 Jul 2020 10:22:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id zVA96MdVEcJe for ; Thu, 16 Jul 2020 10:22:38 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by whitealder.osuosl.org (Postfix) with ESMTPS id 44DB68AFEC for ; Thu, 16 Jul 2020 10:22:38 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 89A51204EA; Thu, 16 Jul 2020 10:22:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594894958; bh=vzEaE1HWTa7LYtbebB7ritpzkpel2YtikBtG3CEZDzU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=O7qT433Bf508kbmPUyZtGJ1ha3eKm5yrmKHurnYxiVO1tk+RfIFdFzfIP9a4dEULJ cxskKb6f2hESv3IlEBT1RUtZQsbEm8i3bC2eetulC0gX+ABbte+A6hbUMZv5oMxo3Z dEeF7i7CvTyJM+Yn2p8YoEk1EHckrb6iEUSt+mB4= Date: Thu, 16 Jul 2020 11:22:33 +0100 From: Will Deacon To: John Garry Subject: Re: [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency Message-ID: <20200716102233.GC7036@willie-the-truck> References: <1592846920-45338-1-git-send-email-john.garry@huawei.com> <20200716101940.GA7036@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200716101940.GA7036@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: trivial@kernel.org, maz@kernel.org, linux-kernel@vger.kernel.org, linuxarm@huawei.com, iommu@lists.linux-foundation.org, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Thu, Jul 16, 2020 at 11:19:41AM +0100, Will Deacon wrote: > On Tue, Jun 23, 2020 at 01:28:36AM +0800, John Garry wrote: > > As mentioned in [0], the CPU may consume many cycles processing > > arm_smmu_cmdq_issue_cmdlist(). One issue we find is the cmpxchg() loop to > > get space on the queue takes approx 25% of the cycles for this function. > > > > This series removes that cmpxchg(). > > How about something much simpler like the diff below? Ah, scratch that, I don't drop the lock if we fail the cas with it held. Let me hack it some more (I have no hardware so I can only build-test this). Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu