Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752954AbaBYM3X (ORCPT ); Tue, 25 Feb 2014 07:29:23 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:50126 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751785AbaBYM3V (ORCPT ); Tue, 25 Feb 2014 07:29:21 -0500 Date: Tue, 25 Feb 2014 12:29:16 +0000 From: Russell King - ARM Linux To: Joel Fernandes Cc: Lars-Peter Clausen , linux-rt-users@vger.kernel.org, Vinod Koul , Linux Kernel Mailing List , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: Ideas/suggestions to avoid repeated locking and reducing too many lists with dmaengine? Message-ID: <20140225122916.GX27282@n2100.arm.linux.org.uk> References: <530B9784.5060904@ti.com> <20140224192152.GV27282@n2100.arm.linux.org.uk> <530BC9F8.2040402@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <530BC9F8.2040402@ti.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 24, 2014 at 04:38:48PM -0600, Joel Fernandes wrote: > Actually I did do some tracing earlier before I posted this thread- and > notice there was excessive traces of locking/unlocking. It is very light > though as you pointed and lighter without debug options. The only other > notable difference is the fact that we are now going through the dmaengine > framework in the newer kernel vs the faster one. Okay, for OMAP, there's additional latency caused by the tasklet which starts a transaction when there's no previous transaction running - that will be your biggest problem. I do want to move omap-dma away from having a fixed binding between claimed channels and the logical channels since that's too wasteful, and that's what the tasklet will eventually be doing - but with omap-dma being divorsed from the old code, this tasklet may not be necessary anymore (since we no longer have to operate in process context for that bit.) There's a huge pile of patches I have queued up for the next merge window in linux-next - I'd rather get these into mainline before trying to do any restructuring, otherwise we're going to get into a hell of a problem with merge conflicts. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- 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/