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 C6AAEC6FA86 for ; Thu, 22 Sep 2022 10:54:15 +0000 (UTC) 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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=UJkXfnS02XNdwWKjGEO+osMARmRwm8N+74/sPPrUouA=; b=uXn6ISl7yqP8DH k4+h6fE8RGmbzyt8TCvf4953CtPnbwRrb7EW3vGdUyiNNq3cHCwPKZp/0UT5QbF3a+hjlLH5xB7pl 1domgiFbAg48QHKPBu/Fx44Ll1JYMicQDHeMwrG5+FM6h26dc47D4Fj5IvQQjHQZt30emoiB9XZKZ lrHPpF0dToky9o+k5Clx/Z+wj9BSH22ga3s4J5735e+WsQhaGb6rEX5AHqtBoR7C/nYelFAvHTrwa 9CMQq/kE66QAgdkWwjO5q3T0WzOOZ0txtgg5OJC2Oua1Mk4z3L0CkHaTLRobsgbTFvoH7bOwSZfkV 9tEtrt4IYTQzBJz4qxjg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1obJpF-00F2Eh-Dy; Thu, 22 Sep 2022 10:53:01 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1obJpB-00F2D7-WE for linux-arm-kernel@lists.infradead.org; Thu, 22 Sep 2022 10:52:59 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4BADDB835BD; Thu, 22 Sep 2022 10:52:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B825C433D6; Thu, 22 Sep 2022 10:52:52 +0000 (UTC) Date: Thu, 22 Sep 2022 11:52:48 +0100 From: Catalin Marinas To: James Clark Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, suzuki.poulose@arm.com, mathieu.poirier@linaro.org, mike.leach@linaro.org, leo.yan@linaro.org, broonie@kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Mark Rutland Subject: Re: [PATCH 0/1] arm64: defconfig: Add Coresight as module Message-ID: References: <20220921140535.152627-1-james.clark@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220922_035258_224567_42F39E65 X-CRM114-Status: GOOD ( 20.18 ) 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Sep 22, 2022 at 10:34:45AM +0100, James Clark wrote: > On 21/09/2022 16:08, Catalin Marinas wrote: > > 2. Always on CONFIG_PID_IN_CONTEXTIDR (we might as well remove the > > Kconfig entry). This would write the root pid namespace value > > (task_pid_nr()). > > If we're not worried about the overhead after all, this would be the > easiest solution. And then SPE or Coresight already decide whether they > want to use the value or not, so no further changes are needed. > > From Leo's patch there is a table that shows a 1% overhead with it > enabled permanently, and I've heard a figure like that mentioned before. > So I could also resurrect that patch to use static keys? Although it's a > bit more complicated, that would be my preference. And then we can have > that mode always on. I don't think we should bother with static keys, just always enable it but try to reduce/group the ISBs from all the functions called on the __switch_to() path. We may actually get a speed-up. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel