Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756655AbYLPAJm (ORCPT ); Mon, 15 Dec 2008 19:09:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753706AbYLPAJa (ORCPT ); Mon, 15 Dec 2008 19:09:30 -0500 Received: from wf-out-1314.google.com ([209.85.200.171]:60793 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753559AbYLPAJ3 (ORCPT ); Mon, 15 Dec 2008 19:09:29 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references:x-google-sender-auth; b=KvYk31MPxKPnxlqWF8/ERXbo/MG7U9PR3fGb0xUExi0iOCeKO6tM3JSBthtq0qnfjL lM+u2of5PltnmtCoQRydtnaFUyTHu8YZXHjAy7uDN+WEK/G4C2WA+EW+UjTJHKfazmUe mceymJI3Hu8BGize9f6OG2zZf6MXfFt2sPCKc= Message-ID: Date: Mon, 15 Dec 2008 17:09:27 -0700 From: "Dan Williams" To: "Sosnowski, Maciej" Subject: Re: [PATCH 11/13] dmaengine: kill struct dma_client and supporting infrastructure Cc: "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "hskinnemoen@atmel.com" , "g.liakhovetski@gmx.de" , "nicolas.ferre@atmel.com" In-Reply-To: <129600E5E5FB004392DDC3FB599660D70C8F3407@irsmsx504.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20081114213300.32354.1154.stgit@dwillia2-linux.ch.intel.com> <20081114213513.32354.58256.stgit@dwillia2-linux.ch.intel.com> <129600E5E5FB004392DDC3FB599660D70C8F3407@irsmsx504.ger.corp.intel.com> X-Google-Sender-Auth: 01d24fc940b64820 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2016 Lines: 52 On Fri, Dec 12, 2008 at 7:29 AM, Sosnowski, Maciej wrote: > Williams, Dan J wrote: >> All users have been converted to either the general-purpose allocator, >> dma_find_channel, or dma_request_channel. >> >> Signed-off-by: Dan Williams >> --- > (...) >> /** >> - * dma_chans_notify_available - broadcast available channels to the >> clients >> - */ >> -static void dma_clients_notify_available(void) >> -{ >> - struct dma_client *client; >> - >> - mutex_lock(&dma_list_mutex); >> - >> - list_for_each_entry(client, &dma_client_list, global_node) >> - dma_client_chan_alloc(client); >> - >> - mutex_unlock(&dma_list_mutex); >> -} > > I agree with Guennadi's concern about removing clients' notification > of new devices available in the system. > I understand that this design is based on polling instead, > however polling is always less efficient approach. > Do you think that restoring notifications in this redesigned dmaengine > would be more painful than limiting clients to polling solution? > You are missing that net_dma has always "polled". Consider the case of how net_dma currently operates prior to ioatdma.ko being loaded. It periodically calls get_softnet_dma() to see if a channel is available, if it does not find one it falls back to a cpu copy. All that has changed is replacing this custom channel allocation routine with the unified dma_find_channel() interface. Channel notifications are not required. Either everything is built-in to guarantee that an engine is available upon request[1], or the client is smart enough to run without a channel for while like net_dma and raid offload. Regards, Dan [1] http://marc.info/?l=linux-kernel&m=122835195303213&w=2 -- 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/