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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 9D921C433E0 for ; Fri, 12 Feb 2021 13:34:13 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 07D9264E6B for ; Fri, 12 Feb 2021 13:34:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07D9264E6B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=Huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id B6F80100EA2DE; Fri, 12 Feb 2021 05:34:12 -0800 (PST) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=185.176.79.56; helo=frasgout.his.huawei.com; envelope-from=jonathan.cameron@huawei.com; receiver= 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 ml01.01.org (Postfix) with ESMTPS id D8B98100EA2D9 for ; Fri, 12 Feb 2021 05:34:09 -0800 (PST) Received: from fraeml711-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4DcZB80s6bz67mLJ; Fri, 12 Feb 2021 21:30:24 +0800 (CST) Received: from lhreml710-chm.china.huawei.com (10.201.108.61) by fraeml711-chm.china.huawei.com (10.206.15.60) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Fri, 12 Feb 2021 14:34:07 +0100 Received: from localhost (10.47.28.230) by lhreml710-chm.china.huawei.com (10.201.108.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Fri, 12 Feb 2021 13:34:06 +0000 Date: Fri, 12 Feb 2021 13:33:04 +0000 From: Jonathan Cameron To: Dan Williams Subject: Re: [PATCH v2 3/8] cxl/mem: Register CXL memX devices Message-ID: <20210212133304.00001f28@Huawei.com> In-Reply-To: References: <20210210000259.635748-1-ben.widawsky@intel.com> <20210210000259.635748-4-ben.widawsky@intel.com> <20210210181725.00007865@Huawei.com> <20210211101746.00005e8c@Huawei.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 X-Originating-IP: [10.47.28.230] X-ClientProxiedBy: lhreml721-chm.china.huawei.com (10.201.108.72) To lhreml710-chm.china.huawei.com (10.201.108.61) X-CFilter-Loop: Reflected Message-ID-Hash: 7FZWL2N3PSRQDEDQV3QK4W47YPEAHPPF X-Message-ID-Hash: 7FZWL2N3PSRQDEDQV3QK4W47YPEAHPPF X-MailFrom: jonathan.cameron@huawei.com X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: Ben Widawsky , linux-cxl@vger.kernel.org, "Linux ACPI , Linux Kernel Mailing List" , linux-nvdimm , Linux PCI , Bjorn Helgaas , Chris Browy , Christoph Hellwig , David Hildenbrand , David Rientjes , Jon Masters , "John Groves (jgroves)" , "Kelley, Sean V" X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, 11 Feb 2021 12:40:45 -0800 Dan Williams wrote: > On Thu, Feb 11, 2021 at 2:19 AM Jonathan Cameron > wrote: > > > > On Wed, 10 Feb 2021 18:17:25 +0000 > > Jonathan Cameron wrote: > > > > > On Tue, 9 Feb 2021 16:02:54 -0800 > > > Ben Widawsky wrote: > > > > > > > From: Dan Williams > > > > > > > > Create the /sys/bus/cxl hierarchy to enumerate: > > > > > > > > * Memory Devices (per-endpoint control devices) > > > > > > > > * Memory Address Space Devices (platform address ranges with > > > > interleaving, performance, and persistence attributes) > > > > > > > > * Memory Regions (active provisioned memory from an address space device > > > > that is in use as System RAM or delegated to libnvdimm as Persistent > > > > Memory regions). > > > > > > > > For now, only the per-endpoint control devices are registered on the > > > > 'cxl' bus. However, going forward it will provide a mechanism to > > > > coordinate cross-device interleave. > > > > > > > > Signed-off-by: Dan Williams > > > > Signed-off-by: Ben Widawsky > > > > > > One stray header, and a request for a tiny bit of reordering to > > > make it easier to chase through creation and destruction. > > > > > > Either way with the header move to earlier patch I'm fine with this one. > > > > > > Reviewed-by: Jonathan Cameron > > > > Actually thinking more on this, what is the justification for the > > complexity + overhead of a percpu_refcount vs a refcount > > A typical refcount does not have the block and drain semantics of a > percpu_ref. I'm planning to circle back and make this a first class > facility of the cdev interface borrowing the debugfs approach [1], but > for now percpu_ref fits the bill locally. > > > I don't think this is a high enough performance path for it to matter. > > Perhaps I'm missing a usecase where it does? > > It's less about percpu_ref performance and more about the > percpu_ref_tryget_live() facility. > > [1]: http://lore.kernel.org/r/CAPcyv4jEYPsyh0bhbtKGRbK3bgp=_+=2rjx4X0gLi5-25VvDyg@mail.gmail.com Thanks for the reference. Definitely a nasty corner to clean up so I'll keep an eye open for a new version of that series. Jonathan _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org