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 10:23:37 +0200 Message-ID: <4E439189.1030905@fusionio.com> References: <20110811004216.GA24810@july> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Shaohua Li Cc: Kyungmin Park , "linux-kernel@vger.kernel.org" , "arnd@arndb.de" , "jh80.chung@samsung.com" , "linux-mmc@vger.kernel.org" List-Id: linux-mmc@vger.kernel.org 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. 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; if (e->ops->elevator_get_req_context_fn) return e->ops->elevator_get_req_context_fn(q, rq); return -1; } and then cfq/others adding that helper to provide the mapping. Context is a bad name, but so is hint. Perhaps app_key would be better, as it more direcly infers what is being returned. -- Jens Axboe