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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id ADE72CAC5A7 for ; Mon, 22 Sep 2025 12:18:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cnoK284wC9IBvGY8v6wVkknfTGfHO/sFr+t4M3yGJFM=; b=JGNyAA5qZuBKE5veg01XOKjbBt WyafmL3S9tXHpfzD2bOkKRJA3uaxIvLGct77Z/Wy62QzPCmJhMpRwEbXgeiH9I9w0vJc02QtP4Lek MdwpNgssGvrXzH9npnpYtImzsQheez/aocmE0n+fhk1+/2kLFoqpTTCe0CRj32+GPKA/epJWuHCDp ql1+Aof9gp7d0qdOybEjWKlpluYDFcD1RDkH51HFPpXeUgxFXmrdgvfdp+8DsZmtoOlbKcd7Z+ZPK YlrfUbsZDbWBEjXgACPuThgxAZXSYj6TldozpJUsbSpRDKifEFPf5BEv2vCQtYCxFyfKeSErP9y8Y H8YstiCQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v0fUf-0000000AIpi-1Qz1; Mon, 22 Sep 2025 12:18:09 +0000 Received: from mailgw.kylinos.cn ([124.126.103.232]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v0fUb-0000000AIoi-1Avf for linux-arm-kernel@lists.infradead.org; Mon, 22 Sep 2025 12:18:08 +0000 X-UUID: 293a636a97ae11f08b9f7d2eb6caa7cf-20250922 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.45,REQID:820a0db1-d8aa-4ccd-a29a-d5a8403565fe,IP:15, URL:0,TC:0,Content:0,EDM:0,RT:0,SF:-40,FILE:0,BULK:0,RULE:Release_Ham,ACTI ON:release,TS:-25 X-CID-INFO: VERSION:1.1.45,REQID:820a0db1-d8aa-4ccd-a29a-d5a8403565fe,IP:15,UR L:0,TC:0,Content:0,EDM:0,RT:0,SF:-40,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:-25 X-CID-META: VersionHash:6493067,CLOUDID:a01a001bb6b5825328af111a4ef35bfd,BulkI D:250922201752257MKIUF,BulkQuantity:0,Recheck:0,SF:10|24|38|44|64|66|78|80 |81|82|83|102|841|850,TC:nil,Content:-10|0|50,EDM:-3,IP:-2,URL:0,File:nil, RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,D KP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 1,FCT|UOG X-CID-BAS: 1,FCT|UOG,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_FSI X-UUID: 293a636a97ae11f08b9f7d2eb6caa7cf-20250922 X-User: pengcan@kylinos.cn Received: from localhost.localdomain [(116.128.244.171)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 1686138324; Mon, 22 Sep 2025 20:17:52 +0800 From: Can Peng To: catalin.marinas@arm.com, will@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] arm/syscalls: mark syscall invocation as Date: Mon, 22 Sep 2025 20:17:30 +0800 Message-Id: <20250922121730.986761-1-pengcan@kylinos.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250922_051805_688659_AC5B0BCC X-CRM114-Status: UNSURE ( 7.33 ) X-CRM114-Notice: Please train this message. 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 Hello, >> The invoke_syscall() function is overwhelmingly called for >> valid system call entries. Annotate the main path with likely() >> to help the compiler generate better branch prediction hints, >> reducing CPU pipeline stalls due to mispredictions. >> >> This is a micro-optimization targeting syscall-heavy workloads. > >Does it actually make a measurable difference? This change implements a micro-optimization. Benchmark results from the Kunpeng 920 machine are as follows: before: - lat_syscall result write call 0.2332 0.2337 0.2341 read call 0.2501 0.2493 0.2506 after: - lat_syscall result write call 0.2301 0.2316 0.2307 read call 0.2492 0.2498 0.2491 Best regards, Can Peng