From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756427Ab2DEXvz (ORCPT ); Thu, 5 Apr 2012 19:51:55 -0400 Received: from casper.infradead.org ([85.118.1.10]:54374 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753016Ab2DEXvy (ORCPT ); Thu, 5 Apr 2012 19:51:54 -0400 Message-ID: <4F7E3011.4090803@kernel.dk> Date: Thu, 05 Apr 2012 17:51:45 -0600 From: Jens Axboe MIME-Version: 1.0 To: Tao Guo CC: Andrew Morton , linux-kernel@vger.kernel.org, neilb@suse.de, axboe@fusionio.com Subject: Re: [PATCH] umem: fix up unplugging. References: <1325254651-15379-1-git-send-email-glorioustao@gmail.com> <20120404144656.7b2a06ec.akpm@linux-foundation.org> <4F7CD6C9.4060509@kernel.dk> In-Reply-To: X-Enigmail-Version: 1.4 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2012-04-04 17:58, Tao Guo wrote: > On Wed, Apr 4, 2012 at 4:18 PM, Jens Axboe wrote: >> On 2012-04-04 16:20, Tao Guo wrote: >>> Hi Andrew, >>> >>> Thanks for your reply. >>> >>> Yes, without this patch the umem driver just doesn't work. >>> It is a bug introduced by commit 7eaceaccab5f40bbfda044629a6298616aeaed50. >>> In that patch, Jens removed the whole mm_unplug_device() function, >>> which used to be >>> the trigger to make umem start to work. >> >> Hmm indeed, that's isn't terribly useful. Why aren't we just calling >> activate_card() on addition of a bio? >> > It is the original design idea, the umem driver also wants to do batch > IO the same as > hard disk drive to fully utilize the IO bandwidth. Sure, just wondering whether the benefits have been tested. But yes, it certainly makes sense. Your patch looks buggy, though. What if the card is currently plugged on another tasks plug list? You seem to assume that it can only be plugged once. -- Jens Axboe