Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966978AbbBDXOo (ORCPT ); Wed, 4 Feb 2015 18:14:44 -0500 Received: from mail-qg0-f52.google.com ([209.85.192.52]:32873 "EHLO mail-qg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966308AbbBDXOm convert rfc822-to-8bit (ORCPT ); Wed, 4 Feb 2015 18:14:42 -0500 MIME-Version: 1.0 In-Reply-To: <54930835.8020009@codeaurora.org> References: <1418854236-25140-1-git-send-email-gregory.0xf0@gmail.com> <54930835.8020009@codeaurora.org> From: Gregory Fong Date: Wed, 4 Feb 2015 15:14:11 -0800 Message-ID: Subject: Re: [RFC PATCH] mm: cma: add functions for getting allocation info To: Laura Abbott Cc: linux-mm@kvack.org, Marek Szyprowski , Michal Nazarewicz , Andrew Morton , Joonsoo Kim , "Aneesh Kumar K.V" , Weijie Yang , Laurent Pinchart , open list , "Stefan I. Strogin" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2283 Lines: 49 On Thu, Dec 18, 2014 at 9:00 AM, Laura Abbott wrote: > On 12/17/2014 2:10 PM, Gregory Fong wrote: >> >> These functions allow for retrieval of information on what is allocated from >> within a given CMA region. It can be useful to know the number of distinct >> contiguous allocations and where in the region those allocations are >> located. >> >> Based on an initial version by Marc Carino in a driver >> that used the CMA bitmap directly; this instead moves the logic into the core >> CMA API. >> >> Signed-off-by: Gregory Fong >> --- >> This has been really useful for us to determine allocation information for a >> CMA region. We have had a separate driver that might not be appropriate for >> upstream, but allowed using a user program to run CMA unit tests to verify that >> allocations end up where they we would expect. This addition would allow for >> that without needing to expose the CMA bitmap. Wanted to put this out there to >> see if anyone else would be interested, comments and suggestions welcome. >> > > Information is definitely useful but I'm not sure how it's intended to > be used. Do you have a sample usage of these APIs? Another option might > be to just add regular debugfs support for each of the regions instead > of just calling out to a separate driver. Sorry for the late reply, got way behind on emails. Some background is probably good to start here: we use CMA to provide very large (hundreds of MiB) contiguous regions for an out-of-kernel allocator to divvy up according to varying platform requirements. It's an unusual configuration but one that we're stuck with for now. After having some time to think about this more and taking into consideration yours and Michał's reply, this definitely does not seem like the proper approach. Something better would probably be like what Stefan is working on[1], so I'll wait to see his v2 that uses debugfs instead. [1] https://lkml.org/lkml/2014/12/26/95 Thanks, Gregory -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/