From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH v3 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able Date: Tue, 30 Jul 2013 11:49:00 -0700 (PDT) Message-ID: <20130730.114900.5636932806999400.davem@davemloft.net> References: <20130730140059.GE27962@kroah.com> <20130730.113329.1450325193505423812.davem@davemloft.net> <1375209677.2075.129.camel@joe-AO722> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: gregkh@linuxfoundation.org, hayeswang@realtek.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, nic_swsd@realtek.com To: joe@perches.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:39693 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756954Ab3G3StA (ORCPT ); Tue, 30 Jul 2013 14:49:00 -0400 In-Reply-To: <1375209677.2075.129.camel@joe-AO722> Sender: netdev-owner@vger.kernel.org List-ID: From: Joe Perches Date: Tue, 30 Jul 2013 11:41:17 -0700 > On Tue, 2013-07-30 at 11:33 -0700, David Miller wrote: >> From: Greg KH >> Date: Tue, 30 Jul 2013 07:00:59 -0700 >> >> > This call is so slow, you can afford to make a call to kmalloc for the >> > data, as it sure just did for other structures it needed :) >> >> I told him to implement things this way, to avoid calling kmalloc every >> single register access. >> >> Using kmalloc all the time makes the access fragile, since a badly timed >> call during high memory pressure can fail. >> >> I'd rather the potential failure happen at one time, probe time. >> >> In any event, Ming Lei has suggested using usbnet_{read,write}_cmd() >> instead, which sounds like a good solution to this problem. > > Those do per-call allocs too. Sigh... Ok I won't fight this any longer then :-)