From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: RE: [PATCH net-next 01/11] sfc: Implement 128-bit writes for efx_writeo_page Date: Thu, 12 Jul 2012 17:10:40 +0100 Message-ID: <1342109440.2662.9.camel@bwh-desktop.uk.solarflarecom.com> References: <1342048389.2613.59.camel@bwh-desktop.uk.solarflarecom.com> <1342048518.2613.60.camel@bwh-desktop.uk.solarflarecom.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , , To: David Laight Return-path: Received: from webmail.solarflare.com ([12.187.104.25]:41556 "EHLO ocex02.SolarFlarecom.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1161220Ab2GLQKr (ORCPT ); Thu, 12 Jul 2012 12:10:47 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2012-07-12 at 09:45 +0100, David Laight wrote: > > From: netdev-owner@vger.kernel.org [mailto:netdev- > > owner@vger.kernel.org] On Behalf Of Ben Hutchings > > Sent: 12 July 2012 00:15 > > To: David Miller > > Cc: netdev@vger.kernel.org; linux-net-drivers@solarflare.com > > Subject: [PATCH net-next 01/11] sfc: Implement 128-bit writes for > > efx_writeo_page > > > > Add support for writing a TX descriptor to the NIC in one PCIe > > transaction on x86_64 machines. > ... > > +static inline void _efx_writeo(struct efx_nic *efx, efx_le_128 value, > > + unsigned int reg) > > +{ > ... > > +} > > Wouldn't it be better to put code this in some generic header > where it can be used by other drivers? I can do that, but I'm not sure that it's all that generic. > Some architectures/cpus have dma engines associated with the > PCIe interface than can be used to request longer PCIe transactions. > > So you probably need a transfer length as well. > > I suspect that it is never worth using an interrupt for > the completion of such dma - although splitting the request > and wait would allow the caller to overlap operations. > > With a dma interface it is worth updating multiple ring > entries at one, and reading multiple entries for status. We're trying to reduce latency. You seem to be talking about batching to increase efficiency at the cost of latency. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.