From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2806419755B for ; Fri, 19 Sep 2025 11:41:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758282062; cv=none; b=k9ZT/ZQ8YT2YS1PuyJ+WVCwk26o/YsUFiiYoTDlsxOUNtXeifaYbfPk8f8NwGM6uGaV7uheWlqTUByiP8qQ+Qzuf0qcecofHBC2+7So3g0Lokd8EUb3KGEihfqSzafDeOxhQr1GE0GyJn3hQ76vY2xXOV7ZDuxBkiJaRGOJUbpM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758282062; c=relaxed/simple; bh=792DYNCBkP3tBnabEABgwGFKr8gigP8l0yyHqaUtcz0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pFGtFJJ7LU8iIZVj1Li/9FSGguAjN8UzLrta2AK0SUaoO4MzCUM75mgeCPSZ+97z3CuDIQ9zZ5rZY9ykzczzQVl9HIjZ3xp5NM5MmaSSFIxTake5UoacJV42LWgdst1J2hSkSURcSnIhuTp77X2WS3SY+JsLx4Aauwq18FckOKw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tP4QNoad; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tP4QNoad" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFF3EC4CEF0; Fri, 19 Sep 2025 11:41:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758282061; bh=792DYNCBkP3tBnabEABgwGFKr8gigP8l0yyHqaUtcz0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tP4QNoadn6CKvqSo+LZcTfeyko5AvnM+HUlQ717kWW5fmRqOuDxDfUGjZZhbAq7EF 4wA7JNCQH3LLZpN9wWcm4RuFmZIhZyolHeBh0pBFTXhvwMaGu14zH/BlvRmqw48343 EEAJuynhEW4VArF/EA3Di9Za6XL/d1jwOhyxHKOuuoIzeXzR446XDbPVNPdwd4ePBR IvORPciwbAPTN/AejQRQ1L7KdM8NfAApvvP25o9uQkd9eIvLGmWPJ/sCnzxNM0NQ7J e46FF1RiATQ8fK5m2NY5F1/iIMDpXlOU6wLT3RVdlXW/L4AgIAYkyIlfada25QLzOW LsaXWlPLLo7Zw== Date: Fri, 19 Sep 2025 12:40:57 +0100 From: Will Deacon To: Can Peng Cc: catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] arm/syscalls: mark syscall invocation as likely in invoke_syscall Message-ID: References: <20250919100042.497861-1-pengcan@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250919100042.497861-1-pengcan@kylinos.cn> On Fri, Sep 19, 2025 at 06:00:42PM +0800, Can Peng wrote: > 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? Will