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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 18F51C4338F for ; Thu, 5 Aug 2021 10:24:42 +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 D220760724 for ; Thu, 5 Aug 2021 10:24:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D220760724 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:CC:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iExAVgPkbIPjkRvcbZutWKyIsu+ic3HAs7RObHC1wSw=; b=Ga4XxjH5Wa7wrKPRrHBYzZ9gK3 oR1hjx7u0Rni510ocwbW6rQJHWdfjqytWxwBWzCLi8NN6fLtUtFHqETzbEt4ZS0p171cA2EIY/w6W SokZu4HhQWpmJ5RnU6uCNN919CxClVWuBA2iww/5KQ1YKbiwi3BS1xfuEimIOjQXrq3wtJhawHoma tG/L3U1DStu1Dt8+Qa4lpI7phuCPbp24BY+9sr70F9J7KpBEjGH3VGHpY7HPsL3pv+zmnuauQJZ9k vU+T2YCyEufAm3fYnGIPsOEUvi1E0ijJwCakykLM/66a38ET6iCzf1oNVxUJb6oUH6ubbEkAql8iY JQBv6OGg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBaWh-0097on-29; Thu, 05 Aug 2021 10:22:59 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBaWc-0097nJ-BE for linux-arm-kernel@lists.infradead.org; Thu, 05 Aug 2021 10:22:56 +0000 Received: from fraeml734-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4GgPn36gKWz6F8JB; Thu, 5 Aug 2021 18:22:31 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml734-chm.china.huawei.com (10.206.15.215) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 5 Aug 2021 12:22:47 +0200 Received: from [10.47.24.8] (10.47.24.8) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Thu, 5 Aug 2021 11:22:46 +0100 Subject: Re: [PATCH] iommu/arm-smmu-v3: Remove some unneeded init in arm_smmu_cmdq_issue_cmdlist() To: , CC: , , , , References: <1624293394-202509-1-git-send-email-john.garry@huawei.com> From: John Garry Message-ID: Date: Thu, 5 Aug 2021 11:22:15 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <1624293394-202509-1-git-send-email-john.garry@huawei.com> Content-Language: en-US X-Originating-IP: [10.47.24.8] X-ClientProxiedBy: lhreml706-chm.china.huawei.com (10.201.108.55) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210805_032254_589026_B54E1D23 X-CRM114-Status: GOOD ( 15.96 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 21/06/2021 17:36, John Garry wrote: > Members of struct "llq" will be zero-inited, apart from member max_n_shift. > But we write llq.val straight after the init, so it was pointless to zero > init those other members. As such, separately init member max_n_shift > only. > > In addition, struct "head" is initialised to "llq" only so that member > max_n_shift is set. But that member is never referenced for "head", so > remove any init there. > > Removing these initializations is seen as a small performance optimisation, > as this code is (very) hot path. > Hi Will, Any chance you can pick up this small optimisation? Cheers > Signed-off-by: John Garry > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > index 54b2f27b81d4..8a8ad49bb7fd 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > @@ -727,11 +727,11 @@ static int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu, > unsigned long flags; > bool owner; > struct arm_smmu_cmdq *cmdq = &smmu->cmdq; > - struct arm_smmu_ll_queue llq = { > - .max_n_shift = cmdq->q.llq.max_n_shift, > - }, head = llq; > + struct arm_smmu_ll_queue llq, head; > int ret = 0; > > + llq.max_n_shift = cmdq->q.llq.max_n_shift; > + > /* 1. Allocate some space in the queue */ > local_irq_save(flags); > llq.val = READ_ONCE(cmdq->q.llq.val); > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel