From patchwork Wed Aug 18 08:04:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 12443569 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=-17.4 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,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 DA024C4338F for ; Wed, 18 Aug 2021 08:08:29 +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 A9E166102A for ; Wed, 18 Aug 2021 08:08:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A9E166102A 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-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=794rd0hcQ5yCE6iBJ60u1gX5agNOSO82mmbm2zGL8YM=; b=r34INioHsDqo+s IqfRZwxqROCkmUxAgCLxJNZvgyZ7qOmTOBOncefj+9Mht4cLORO26bXd/7PO+xmUoIPNj4x50/uUv 8Jnm6kxN31YMJ+L8KaA62oGriZNyzh88CcMhdTI1ZXPg7F2CRjvg5NIoEmsfNg/ii359WrTzja2pp 72Rn1Qx5nqB8IC8XhPa0jG3s/Td701NTRQG9QhWU49TVzJRMgAGFRs+pZ4W8oQ/QZHE8vKPDhrPiT 52O86qk2MPMdzucmxqOMTfCDDNHQHxvTDnGyDxF4HbopErkw+asu63XOIZKEScPJLHw0KPbxOcLZk H4S64DvT/G5pPnzZJG+A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mGGaV-004ZY5-Kc; Wed, 18 Aug 2021 08:06:15 +0000 Received: from szxga08-in.huawei.com ([45.249.212.255]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mGGa7-004ZSZ-Ui for linux-arm-kernel@lists.infradead.org; Wed, 18 Aug 2021 08:05:53 +0000 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4GqL6s18Sbz1CXBn; Wed, 18 Aug 2021 16:05:25 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 18 Aug 2021 16:05:49 +0800 Received: from thunder-town.china.huawei.com (10.174.178.242) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 18 Aug 2021 16:05:48 +0800 From: Zhen Lei To: Will Deacon , Robin Murphy , "Joerg Roedel" , linux-arm-kernel , iommu , CC: Zhen Lei , John Garry Subject: [PATCH v2 2/2] iommu/arm-smmu-v3: Simplify useless instructions in arm_smmu_cmdq_build_cmd() Date: Wed, 18 Aug 2021 16:04:52 +0800 Message-ID: <20210818080452.2079-3-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.26.0.windows.1 In-Reply-To: <20210818080452.2079-1-thunder.leizhen@huawei.com> References: <20210818080452.2079-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.242] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210818_010552_279618_0766948D X-CRM114-Status: GOOD ( 14.01 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Although the parameter 'cmd' is always passed by a local array variable, and only this function modifies it, the compiler does not know this. The compiler almost always reads the value of cmd[i] from memory rather than directly using the value cached in the register. This generates many useless instruction operations and affects the performance to some extent. To guide the compiler for proper optimization, 'cmd' is defined as a local array variable, marked as register, and copied to the output parameter at a time when the function is returned. The optimization effect can be viewed by running the "size arm-smmu-v3.o" command. Before: text data bss dec hex 26954 1348 56 28358 6ec6 After: text data bss dec hex 26762 1348 56 28166 6e06 Signed-off-by: Zhen Lei --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) 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 01e95b56ffa07d1..7cec0c967f71d86 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -234,10 +234,12 @@ static int queue_remove_raw(struct arm_smmu_queue *q, u64 *ent) } /* High-level queue accessors */ -static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) +static int arm_smmu_cmdq_build_cmd(u64 *out_cmd, struct arm_smmu_cmdq_ent *ent) { - memset(cmd, 0, 1 << CMDQ_ENT_SZ_SHIFT); - cmd[0] |= FIELD_PREP(CMDQ_0_OP, ent->opcode); + register u64 cmd[CMDQ_ENT_DWORDS]; + + cmd[0] = FIELD_PREP(CMDQ_0_OP, ent->opcode); + cmd[1] = 0; switch (ent->opcode) { case CMDQ_OP_TLBI_EL2_ALL: @@ -332,6 +334,9 @@ static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) return -ENOENT; } + out_cmd[0] = cmd[0]; + out_cmd[1] = cmd[1]; + return 0; }