From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964858AbbLHK4b (ORCPT ); Tue, 8 Dec 2015 05:56:31 -0500 Received: from mail-oi0-f49.google.com ([209.85.218.49]:34860 "EHLO mail-oi0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932904AbbLHK42 (ORCPT ); Tue, 8 Dec 2015 05:56:28 -0500 MIME-Version: 1.0 In-Reply-To: <5661F449.5020205@gmail.com> References: <20151129.210210.1777978635596463961.davem@davemloft.net> <20151130.112500.293198684175670933.davem@redhat.com> <5661F449.5020205@gmail.com> Date: Tue, 8 Dec 2015 11:56:28 +0100 Message-ID: Subject: Re: [PATCH 00/13] mvneta Buffer Management and enhancements From: Marcin Wojtas To: David Miller Cc: Florian Fainelli , linux-kernel@vger.kernel.org, "linux-arm-kernel@lists.infradead.org" , netdev@vger.kernel.org, Thomas Petazzoni , Andrew Lunn , Russell King - ARM Linux , Jason Cooper , Yair Mahalalel , Grzegorz Jaszczyk , Simon Guinot , Evan Wang , nadavh@marvell.com, Lior Amsalem , Tomasz Nowicki , =?UTF-8?Q?Gregory_Cl=C3=A9ment?= , nitroshift@yahoo.com, Sebastian Hesselbarth Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi David, 2015-12-04 21:15 GMT+01:00 Florian Fainelli : > (no top posting please) > > On 02/12/15 00:26, Marcin Wojtas wrote: >> Hi Florian, >> >> Can you please describe in more details, what would you expect from >> such special abstraction layer regarding buffer managers? I'd like to >> understand more of your expectations and evaluate possible work. > > Well, something along these lines: > > - have the ability to register a particular pool (location + number of > buffers) in a way that is relatively device agnostic (initialization > would of course be device specific) > > - provide a set of buffer management APIs like those you proposed below, > and have some generic code that leverages what > drivers/net/ethernet/sun/niu.c does for instance > > - introduce a netdev_alloc_skb_from_pool() or something like that which > would limit the amount of code to change in your network driver to > benefit from that feature so based > > I am sure David would be able to suggest more detailed API. > As we're getting closer to what a generic BM part, could you please share your thoughts on the possible API? >>> >>>> What kind of abstraction and helpers do you mean? Some kind of API >>>> (e.g. bm_alloc_buffer, bm_initialize_ring bm_put_buffer, >>>> bm_get_buffer), which would be used by platform drivers (and specific >>>> aplications if one wants to develop on top of the kernel)? >>>> >>>> In general, what is your top-view of such solution and its cooperation >>>> with the drivers? >>> >>> The tricky parts involved have to do with allocating pages for the >>> buffer pools and minimizing the number of atomic refcounting >>> operations on those pages for for the puts and gets, particularly >>> around buffer replenish runs. >>> >>> For example, if you're allocating a page for a buffer pool the device >>> will chop into N (for any N < PAGE_SIZE) byte pieces, you can >>> eliminate many atomic operations. > Do you think you can point to anything similar that could be a sort of reference for such solution? Best regards, Marcin