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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5FAD3C43441 for ; Mon, 26 Nov 2018 19:56:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AE1620664 for ; Mon, 26 Nov 2018 19:56:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2AE1620664 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726627AbeK0GwG (ORCPT ); Tue, 27 Nov 2018 01:52:06 -0500 Received: from mga09.intel.com ([134.134.136.24]:24371 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726251AbeK0GwG (ORCPT ); Tue, 27 Nov 2018 01:52:06 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Nov 2018 11:56:54 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,283,1539673200"; d="scan'208";a="252898133" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by orsmga004.jf.intel.com with ESMTP; 26 Nov 2018 11:56:54 -0800 Date: Mon, 26 Nov 2018 12:53:53 -0700 From: Keith Busch To: Greg Kroah-Hartman Cc: "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "linux-mm@kvack.org" , Rafael Wysocki , "Hansen, Dave" , "Williams, Dan J" Subject: Re: [PATCH 4/7] node: Add memory caching attributes Message-ID: <20181126195352.GS26707@localhost.localdomain> References: <20181114224921.12123-2-keith.busch@intel.com> <20181114224921.12123-5-keith.busch@intel.com> <20181126190619.GA32595@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181126190619.GA32595@kroah.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 26, 2018 at 11:06:19AM -0800, Greg Kroah-Hartman wrote: > On Wed, Nov 14, 2018 at 03:49:17PM -0700, Keith Busch wrote: > > System memory may have side caches to help improve access speed. While > > the system provided cache is transparent to the software accessing > > these memory ranges, applications can optimize their own access based > > on cache attributes. > > > > In preparation for such systems, provide a new API for the kernel to > > register these memory side caches under the memory node that provides it. > > > > The kernel's sysfs representation is modeled from the cpu cacheinfo > > attributes, as seen from /sys/devices/system/cpu/cpuX/cache/. Unlike CPU > > cacheinfo, though, a higher node's memory cache level is nearer to the > > CPU, while lower levels are closer to the backing memory. Also unlike > > CPU cache, the system handles flushing any dirty cached memory to the > > last level the memory on a power failure if the range is persistent. > > > > The exported attributes are the cache size, the line size, associativity, > > and write back policy. > > > > Signed-off-by: Keith Busch > > --- > > drivers/base/node.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > include/linux/node.h | 23 ++++++++++ > > 2 files changed, 140 insertions(+) > > > > diff --git a/drivers/base/node.c b/drivers/base/node.c > > index 232535761998..bb94f1d18115 100644 > > --- a/drivers/base/node.c > > +++ b/drivers/base/node.c > > @@ -60,6 +60,12 @@ static DEVICE_ATTR(cpumap, S_IRUGO, node_read_cpumask, NULL); > > static DEVICE_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL); > > > > #ifdef CONFIG_HMEM > > +struct node_cache_obj { > > + struct kobject kobj; > > + struct list_head node; > > + struct node_cache_attrs cache_attrs; > > +}; > > I know you all are off in the weeds designing some new crazy api for > this instead of this current proposal (sorry, I lost the thread, I'll > wait for the patches before commenting on it), but I do want to say one > thing here. > > NEVER use a raw kobject as a child for a 'struct device' unless you > REALLY REALLY REALLY REALLY know what you are doing and have a VERY good > reason to do so. > > Just use a 'struct device', otherwise you end up having to reinvent all > of the core logic that struct device provides you, like attribute > callbacks (which you had to create), and other good stuff like telling > userspace that a device has shown up so it knows to look at it. > > That last one is key, a kobject is suddenly a "black hole" in sysfs as > far as userspace knows because it does not see them for the most part > (unless you are mucking around in the filesystem on your own, and > really, don't do that, use a library like the rest of the world unless > you really like reinventing everything, which, from your patchset it > feels like...) > > Anyway, use 'struct device'. That's all. > > greg k-h Okay, thank you for the advice. I prefer to reuse over reinvent. :) I only used kobject because the power/ directory was automatically created with 'struct device', but I now I see there are better ways to suppress that.