From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f197.google.com (mail-io0-f197.google.com [209.85.223.197]) by kanga.kvack.org (Postfix) with ESMTP id CCC546B0387 for ; Thu, 2 Mar 2017 12:00:58 -0500 (EST) Received: by mail-io0-f197.google.com with SMTP id f84so76128150ioj.6 for ; Thu, 02 Mar 2017 09:00:58 -0800 (PST) Received: from resqmta-ch2-09v.sys.comcast.net (resqmta-ch2-09v.sys.comcast.net. [2001:558:fe21:29:69:252:207:41]) by mx.google.com with ESMTPS id y204si6273664iof.62.2017.03.02.09.00.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 02 Mar 2017 09:00:56 -0800 (PST) Date: Thu, 2 Mar 2017 11:00:52 -0600 (CST) From: Christoph Lameter Subject: Re: [LSF/MM TOPIC] Movable memory and reliable higher order allocations In-Reply-To: <20170228231733.GI16328@bombadil.infradead.org> Message-ID: References: <20170228231733.GI16328@bombadil.infradead.org> Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: linux-mm@kvack.org, Jesper Dangaard Brouer , riel@redhat.com, Mel Gorman On Tue, 28 Feb 2017, Matthew Wilcox wrote: > The radix tree is not movable given its current API. In order to move > a node, we need to be able to lock the tree to prevent simultaneous > modification by another CPU. But the radix tree API makes callers > responsible for their own locking -- we don't even know if it's locked > by a mutex or a spinlock, much less which lock protects this tree. > > This was one of my motivations for the xarray. The xarray handles its own > locking, so we can always lock out other CPUs from modifying the array. > We still have to take care of RCU walkers, but that's straightforward > to handle. I have a prototype patch for the radix tree (ignoring the > locking problem), so I can port that over to the xarray and post that > for comment tomorrow. Great. Thanks. -- 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