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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23D9AC54EE9 for ; Thu, 22 Sep 2022 13:06:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230459AbiIVNGu (ORCPT ); Thu, 22 Sep 2022 09:06:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229704AbiIVNGq (ORCPT ); Thu, 22 Sep 2022 09:06:46 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id CD799EBBC0 for ; Thu, 22 Sep 2022 06:06:45 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 29F8A1595; Thu, 22 Sep 2022 06:06:52 -0700 (PDT) Received: from [10.57.1.91] (unknown [10.57.1.91]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0ACD83F73B; Thu, 22 Sep 2022 06:06:43 -0700 (PDT) Message-ID: <489f42fc-2ec1-510b-6f3f-017ee10ee7d2@arm.com> Date: Thu, 22 Sep 2022 14:06:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH 0/1] arm64: defconfig: Add Coresight as module Content-Language: en-US To: Catalin Marinas 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 References: <20220921140535.152627-1-james.clark@arm.com> From: James Clark In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/09/2022 11:52, Catalin Marinas wrote: > 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. > Ok thanks I will take a look at this