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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 C85FBC4338F for ; Wed, 18 Aug 2021 08:06:01 +0000 (UTC) Received: from smtp2.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 7A13160F39 for ; Wed, 18 Aug 2021 08:06:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7A13160F39 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 39F8140265; Wed, 18 Aug 2021 08:06:01 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id UFiRwn1AD2su; Wed, 18 Aug 2021 08:05:57 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp2.osuosl.org (Postfix) with ESMTPS id DC02740475; Wed, 18 Aug 2021 08:05:56 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id B811FC001A; Wed, 18 Aug 2021 08:05:56 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 8F62FC000E for ; Wed, 18 Aug 2021 08:05:53 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 7E7E380D91 for ; Wed, 18 Aug 2021 08:05:53 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id bGUGjbplM_7z for ; Wed, 18 Aug 2021 08:05:52 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by smtp1.osuosl.org (Postfix) with ESMTPS id C30D480D60 for ; Wed, 18 Aug 2021 08:05:51 +0000 (UTC) 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 , 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-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" 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; } -- 2.26.0.106.g9fadedd _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu