From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752507AbbHMNXn (ORCPT ); Thu, 13 Aug 2015 09:23:43 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:33359 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbbHMNXl (ORCPT ); Thu, 13 Aug 2015 09:23:41 -0400 Message-ID: <55CC9A5A.1020209@plexistor.com> Date: Thu, 13 Aug 2015 16:23:38 +0300 From: Boaz Harrosh User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Dan Williams , Boaz Harrosh CC: "linux-kernel@vger.kernel.org" , Jens Axboe , Rik van Riel , "linux-nvdimm@lists.01.org" , Linux MM , Mel Gorman , "torvalds@linux-foundation.org" , Christoph Hellwig Subject: Re: [PATCH v5 2/5] allow mapping page-less memremaped areas into KVA References: <20150813025112.36703.21333.stgit@otcpl-skl-sds-2.jf.intel.com> <20150813030109.36703.21738.stgit@otcpl-skl-sds-2.jf.intel.com> <55CC3222.5090503@plexistor.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/13/2015 03:57 PM, Dan Williams wrote: <> > This is explicitly addressed in the changelog, repeated here: > >> The __pfn_t to resource lookup is indeed inefficient walking of a linked list, >> but there are two mitigating factors: >> >> 1/ The number of persistent memory ranges is bounded by the number of >> DIMMs which is on the order of 10s of DIMMs, not hundreds. >> You do not get where I'm comming from. It used to be a [ptr - ONE_BASE + OTHER_BASE] (In 64 bit) it is now a call and a loop and a search. how ever you will look at it is *not* the instantaneous address translation it is now. I have memory I want memory speeds. You keep thinking HD speeds, where what ever you do will not matter. >> 2/ The lookup yields the entire range, if it becomes inefficient to do a >> kmap_atomic_pfn_t() a PAGE_SIZE at a time the caller can take >> advantage of the fact that the lookup can be amortized for all kmap >> operations it needs to perform in a given range. > What "given range" how can a bdev assume that the all sg-list belongs to the same "range". In fact our code does multple-pmem devices for a long time. What about say md-of-pmems for example, or btrfs > DAX as is is races against pmem unbind. A synchronization cost must > be paid somewhere to make sure the memremap() mapping is still valid. Sorry for being so slow, is what I asked. what is exactly "pmem unbind" ? Currently in my 4.1 Kernel the ioremap is done on modprobe time and released modprobe --remove time. the --remove can not happen with a mounted FS dax or not. So what is exactly "pmem unbind". And if there is a new knob then make it refuse with a raised refcount. Cheers Boaz