From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (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 EBEFF13AA2E; Fri, 2 May 2025 08:45:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746175549; cv=none; b=uJhcl1M96zINah4rY85XonAchn6D4UxKYNFXARH14X6UPHD9PLk+29pXE66usY/wTPdNoaV/O2QPIJqniCQDv+pI30Jufz52Ev7FIxpLzAWM/QVAS2SKQBDkdOrO/6IYLAC6CcBNCjyxd1EV4WJbikEJqFBkN89eBTZzxmp1eI4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746175549; c=relaxed/simple; bh=zu0ac8LDjm74lHe3jv8tdxV6DkSiqZ3HGWixAXATcZ0=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=guNRdL9GSo4lfM0Cbj/5jePJnFQj5xbxIw0VBYBxGA5ebJ7zWp6WmgAZ8zT+Cc+PfcM2p9MP3YYdQ/n8pkkILicE1aa3UuGC/VVNAFy2qgzBT214o6BQlj6V0OJGPBFr5EyZZIuBBq1HuXpzHT/Q48H4pZindoSTDJyAj79TZHM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.18.186.231]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4ZpkwQ2XVqz6L4xM; Fri, 2 May 2025 16:43:34 +0800 (CST) Received: from frapeml500007.china.huawei.com (unknown [7.182.85.172]) by mail.maildlp.com (Postfix) with ESMTPS id 76EC41400D9; Fri, 2 May 2025 16:45:45 +0800 (CST) Received: from P_UKIT01-A7bmah.china.huawei.com (10.126.168.187) by frapeml500007.china.huawei.com (7.182.85.172) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Fri, 2 May 2025 10:45:44 +0200 From: To: , , , , , , , CC: , , , , , , , , , , , , , , Subject: [PATCH v4 1/8] EDAC: Update documentation for the CXL memory patrol scrub control feature Date: Fri, 2 May 2025 09:45:09 +0100 Message-ID: <20250502084517.680-2-shiju.jose@huawei.com> X-Mailer: git-send-email 2.43.0.windows.1 In-Reply-To: <20250502084517.680-1-shiju.jose@huawei.com> References: <20250502084517.680-1-shiju.jose@huawei.com> Precedence: bulk X-Mailing-List: linux-edac@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: lhrpeml500011.china.huawei.com (7.191.174.215) To frapeml500007.china.huawei.com (7.182.85.172) From: Shiju Jose Update the Documentation/edac/scrub.rst to include use cases and policies for CXL memory device-based, CXL region-based patrol scrub control and CXL Error Check Scrub (ECS). Signed-off-by: Shiju Jose --- Documentation/edac/scrub.rst | 76 ++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) diff --git a/Documentation/edac/scrub.rst b/Documentation/edac/scrub.rst index daab929cdba1..89a33ef3fde3 100644 --- a/Documentation/edac/scrub.rst +++ b/Documentation/edac/scrub.rst @@ -264,3 +264,79 @@ Sysfs files are documented in `Documentation/ABI/testing/sysfs-edac-scrub` `Documentation/ABI/testing/sysfs-edac-ecs` + +Examples +-------- + +The usage takes the form shown in these examples: + +1. CXL memory Patrol Scrub + +The following are the use cases identified why we might increase the scrub rate. + +- Scrubbing is needed at device granularity because a device is showing + unexpectedly high errors. + +- Scrubbing may apply to memory that isn't online at all yet. Likely this + is a system wide default setting on boot. + +- Scrubbing at a higher rate because the monitor software has determined that + more reliability is necessary for a particular data set. This is called + Differentiated Reliability. + +1.1. Device based scrubbing + +CXL memory is exposed to memory management subsystem and ultimately userspace +via CXL devices. Device-based scrubbing is used for the first use case +described in "Section 1 CXL Memory Patrol Scrub". + +When combining control via the device interfaces and region interfaces, +"see Section 1.2 Region based scrubbing". + +Sysfs files for scrubbing are documented in +`Documentation/ABI/testing/sysfs-edac-scrub` + +1.2. Region based scrubbing + +CXL memory is exposed to memory management subsystem and ultimately userspace +via CXL regions. CXL Regions represent mapped memory capacity in system +physical address space. These can incorporate one or more parts of multiple CXL +memory devices with traffic interleaved across them. The user may want to control +the scrub rate via this more abstract region instead of having to figure out the +constituent devices and program them separately. The scrub rate for each device +covers the whole device. Thus if multiple regions use parts of that device then +requests for scrubbing of other regions may result in a higher scrub rate than +requested for this specific region. + +Region-based scrubbing is used for the third use case described in +"Section 1 CXL Memory Patrol Scrub". + +Userspace must follow below set of rules on how to set the scrub rates for any +mixture of requirements. + +1. Taking each region in turn from lowest desired scrub rate to highest and set + their scrub rates. Later regions may override the scrub rate on individual + devices (and hence potentially whole regions). + +2. Take each device for which enhanced scrubbing is required (higher rate) and + set those scrub rates. This will override the scrub rates of individual devices, + setting them to the maximum rate required for any of the regions they help back, + unless a specific rate is already defined. + +Sysfs files for scrubbing are documented in +`Documentation/ABI/testing/sysfs-edac-scrub` + +2. CXL memory Error Check Scrub (ECS) + +The Error Check Scrub (ECS) feature enables a memory device to perform error +checking and correction (ECC) and count single-bit errors. The associated +memory controller sets the ECS mode with a trigger sent to the memory +device. CXL ECS control, allows the host, thus the userspace, to change the +attributes for error count mode, threshold number of errors per segment +(indicating how many segments have at least that number of errors) for +reporting errors, and reset the ECS counter. Thus, the responsibility for +initiating Error Check Scrub on a memory device may lie with the memory +controller or platform when unexpectedly high error rates are detected. + +Sysfs files for scrubbing are documented in +`Documentation/ABI/testing/sysfs-edac-ecs` -- 2.43.0