From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f177.google.com (mail-lb0-f177.google.com [209.85.217.177]) by kanga.kvack.org (Postfix) with ESMTP id 41B226B0038 for ; Thu, 13 Aug 2015 09:23:43 -0400 (EDT) Received: by lbbpu9 with SMTP id pu9so26976322lbb.3 for ; Thu, 13 Aug 2015 06:23:42 -0700 (PDT) Received: from mail-wi0-f169.google.com (mail-wi0-f169.google.com. [209.85.212.169]) by mx.google.com with ESMTPS id u10si3945525wiv.111.2015.08.13.06.23.41 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Aug 2015 06:23:41 -0700 (PDT) Received: by wicja10 with SMTP id ja10so151405585wic.1 for ; Thu, 13 Aug 2015 06:23:41 -0700 (PDT) Message-ID: <55CC9A5A.1020209@plexistor.com> Date: Thu, 13 Aug 2015 16:23:38 +0300 From: Boaz Harrosh MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org