From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-x243.google.com (mail-it0-x243.google.com [IPv6:2607:f8b0:4001:c0b::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 28AC82111FE4C for ; Wed, 5 Sep 2018 12:26:56 -0700 (PDT) Received: by mail-it0-x243.google.com with SMTP id h23-v6so10971053ita.5 for ; Wed, 05 Sep 2018 12:26:55 -0700 (PDT) Subject: Re: [PATCH v5 07/13] block: Add PCI P2P flag for request queue and check support for requests References: <20180830185352.3369-1-logang@deltatee.com> <20180830185352.3369-8-logang@deltatee.com> <20180901082812.GB670@lst.de> <5f79c012-c6e1-56bb-62fd-0689181fb2c9@deltatee.com> From: Jens Axboe Message-ID: <59b28977-8f2a-6228-2050-03fae6bdbedd@kernel.dk> Date: Wed, 5 Sep 2018 13:26:51 -0600 MIME-Version: 1.0 In-Reply-To: <5f79c012-c6e1-56bb-62fd-0689181fb2c9@deltatee.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Logan Gunthorpe , Christoph Hellwig Cc: Alex Williamson , linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jason Gunthorpe , Benjamin Herrenschmidt , Bjorn Helgaas , Max Gurtovoy , =?UTF-8?Q?Christian_K=c3=b6nig?= List-ID: On 9/3/18 4:26 PM, Logan Gunthorpe wrote: > > > On 01/09/18 02:28 AM, Christoph Hellwig wrote: >> On Thu, Aug 30, 2018 at 01:11:18PM -0600, Jens Axboe wrote: >>> I think this belongs in the caller - both the validity check, and >>> passing in NOMERGE for this type of request. I don't want to impose >>> this overhead on everything, for a pretty niche case. >> >> It is just a single branch, which will be predicted as not taken >> for non-P2P users. The benefit is that we get proper error checking >> by doing it in the block code. > > I personally agree with Christoph. But if there's consensus in the other > direction or this is a real blocker moving this forward, I can remove it > for the next version. It's a simple branch because the check isn't exhaustive. It just checks the first page. At that point you may as well just require the caller to flag the bio/rq as being P2P, and then do a check for P2P compatibility with the queue. -- Jens Axboe _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm