Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757319AbZCEQpx (ORCPT ); Thu, 5 Mar 2009 11:45:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754374AbZCEQpo (ORCPT ); Thu, 5 Mar 2009 11:45:44 -0500 Received: from vervifontaine.sonytel.be ([80.88.33.193]:50127 "EHLO vervifontaine.sonycom.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754180AbZCEQpo (ORCPT ); Thu, 5 Mar 2009 11:45:44 -0500 Date: Thu, 5 Mar 2009 17:45:39 +0100 (CET) From: Geert Uytterhoeven To: Jens Axboe cc: Benjamin Herrenschmidt , Jim Paris , Vivien Chappelier , David Woodhouse , Arnd Bergmann , Geoff Levand , Linux/PPC Development , Cell Broadband Engine OSS Development , Linux Kernel Development , linux-mtd@lists.infradead.org Subject: Re: [PATCH/RFC] ps3/block: Add ps3vram-ng driver for accessing video RAM as block device In-Reply-To: <20090305110940.GY11787@kernel.dk> Message-ID: References: <20090305083701.GQ11787@kernel.dk> <20090305110940.GY11787@kernel.dk> User-Agent: Alpine 2.00 (LRH 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-15 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3400 Lines: 104 On Thu, 5 Mar 2009, Jens Axboe wrote: > On Thu, Mar 05 2009, Geert Uytterhoeven wrote: > > On Thu, 5 Mar 2009, Jens Axboe wrote: > > > On Wed, Mar 04 2009, Geert Uytterhoeven wrote: > > > > Below is the rewrite of the PS3 Video RAM Storage Driver as a plain block > > > > device, as requested by Arnd Bergmann. > > > I'd rewrite this as a ->make_request_fn handler instead. Then you can > > > get rid of the kernel thread. IOW, change > > > > > > queue = blk_init_queue(ps3vram_request, &priv->lock); > > > > > > to > > > > > > queue = blk_alloc_queue(GFP_KERNEL); > > > blk_queue_make_request(queue, ps3vram_make_request); > > > > Thanks, I didn't know that part... > > > > > Add error handling of course, and call blk_queue_max_*() to set your > > > limits for this device. > > > > I took out the blk_queue_max_*() calls (compared to ps3disk.c), as > > none of the limits apply, and the defaults are fine. > > > > Is that OK, or is it better to make it explicit? > > I think it's always good to make it explicit. Plus for this case you > definitely need it, as blk_init_queue() wont do it for you anymore. blk_queue_make_request() does it for me, too: void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) { ... blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); ... blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE); ... blk_queue_max_sectors(q, SAFE_MAX_SECTORS); ... } struct request_queue * blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id) { ... blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE); blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); ... } > > > Then add a ps3vram_make_request() ala: > > > > > static void ps3vram_do_request(struct request_queue *q, struct bio *bio) > > > { > > > } > > > > > > I just typed it here, so if it doesn't compile you get to keep the > > > pieces :-) > > > > OK, I'll give it a try... > > > > BTW, does this mean the `simple' way, which I used based on LDD3, is > > deprecated? > > Depends.. It's obviously not a very effective approach, since you punt > to a thread for each request. But if you need the IO scheduler helping > you with merging and sorting (for a rotational device), it still has > some merit. For this particular case, the ->make_request_fn approach is > much better. Without the thread, performance indeed increased. But then I noticed ps3vram_make_request() may be called concurrently, so I had to add a mutex to avoid data corruption. This slows the driver down, and in the end, the version with a thread turns out to be ca. 1% faster. The version without a thread is about 50 lines less code, though. With kind regards, Geert Uytterhoeven Software Architect Sony Techsoft Centre Europe The Corporate Village ? Da Vincilaan 7-D1 ? B-1935 Zaventem ? Belgium Phone: +32 (0)2 700 8453 Fax: +32 (0)2 700 8622 E-mail: Geert.Uytterhoeven@sonycom.com Internet: http://www.sony-europe.com/ A division of Sony Europe (Belgium) N.V. VAT BE 0413.825.160 ? RPR Brussels Fortis ? BIC GEBABEBB ? IBAN BE41293037680010 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/