From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [RFC PATCH v2] Add new elevator ops for request hint Date: Thu, 11 Aug 2011 11:01:22 +0200 Message-ID: <4E439A62.8080201@fusionio.com> References: <20110811004216.GA24810@july> <4E439189.1030905@fusionio.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.fusionio.com ([66.114.96.30]:35993 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752041Ab1HKJB1 (ORCPT ); Thu, 11 Aug 2011 05:01:27 -0400 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Kyungmin Park Cc: Shaohua Li , "linux-kernel@vger.kernel.org" , "arnd@arndb.de" , "jh80.chung@samsung.com" , "linux-mmc@vger.kernel.org" On 2011-08-11 10:56, Kyungmin Park wrote: > On Thu, Aug 11, 2011 at 5:23 PM, Jens Axboe wrote: >> On 2011-08-11 03:14, Shaohua Li wrote: >>> 2011/8/11 Shaohua Li : >>>> 2011/8/11 Kyungmin Park : >>>>> Hi Jens >>>>> >>>>> Now eMMC device requires the upper layer information to improve the data >>>>> performance and reliability. >>>>> >>>>> . Context ID >>>>> Using the context information, it can sort out the data internally and improve the performance. >>>>> The main problem is that it's needed to define "What's the context". >>>>> Actually I expect cfq queue has own unique ID but it doesn't so decide to use the pid instead >>>>> >>>>> . Data Tag >>>>> Using the Data Tag (1-bit information), It writes the data at SLC area when it's hot data. So it can make the chip more reliable. >>>>> First I expect the REQ_META but current ext4 doesn't pass the WRITE_META. only use the READ_META. so it needs to investigate it. >>>>> >>>>> With these characteristics, it's helpful to teach the device. After some consideration. it's needed to pass out these information at request data structure. >>>>> >>>>> Sample usage is following in drivers/mmc/card/block.c >>>>> >>>>> struct elevator_queue *e = md->queue.queue->elevator; >>>>> struct request_hint hint; >>>>> int ret; >>>>> >>>>> if (e->ops->elevator_get_req_hint_fn && req) >>>>> ret = e->ops->elevator_get_req_hint_fn(req, &hint); >>>> please put this to blkdev.h or similar. directly using it here >>>> is abnormal. >>> BTW, we can add a (rq->cmd_flags & REQ_ELVPRIV) check here to make >>> sure the request is at io scheduler. >> >> Yep, that should all go inside elv_get_request_context() or whatever is >> a good name. I don't want the hint structure, the caller can just check >> the request flags himself. > Okay I see, it has to modify the filesystem to send the meta request, > REQ_META flags to know it from device drivers. Right, the submitter if the IO is the one that has to decide what is hot or not. >> So something like: >> >> int elv_get_request_context(struct request_queue *q, struct request *rq) >> { >> struct elevator_queue *e = q->elevator; >> >> if (!(rq->cmd_flags & REQ_ELVPRIV)) >> return -1; > Also need to check the !rq case, mmc send the NULL request to wait the > previous request wait. No, that would be a usage bug. -- Jens Axboe