From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russ Anderson Date: Fri, 02 May 2008 17:30:17 +0000 Subject: Re: [PATCH 3/3] ia64: Call migration code on correctable errors v2 Message-Id: <20080502173017.GF7246@sgi.com> List-Id: References: <20080502004425.GD12006@sgi.com> <84144f020805020258x56d4f915u5d826d8f19294d62@mail.gmail.com> <20080502164044.GB7246@sgi.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Pekka J Enberg Cc: linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, Linus Torvalds , Andrew Morton , Tony Luck , Christoph Lameter , gregkh@suse.de On Fri, May 02, 2008 at 07:57:44PM +0300, Pekka J Enberg wrote: > Hi Russ, > > On Fri, 2 May 2008, Russ Anderson wrote: > > > I think sparse and checkpatch would have caught most of these but here goes: > > > > I did run checkpatch.pl. The two warnings were a false positive and > > the other I let slide. I'll make the rest of your suggested changes. > > > > WARNING: consider using strict_strtoul in preference to simple_strtoul > > #340: FILE: arch/ia64/kernel/cpe_migrate.c:301: > > + opt = simple_strtoul(optstr, NULL, 0); > > Why do you think this is a false positive? The false positive is: --- WARNING: Use #include instead of #77: FILE: arch/ia64/kernel/cpe_migrate.c:40: +#include --- linux/mca.h is a different file than asm-ia64/mca.h, so using instead of will cause build problems. > We just converted SLUB over to > use strict_stroul() as suggested by Andrew. I'll use strict_stroul(). > > > > + if (cpe_paddr[cpe_head] = 0) { > > > > + cpe_paddr[cpe_head] = paddr; > > > > + cpe_node[cpe_head] = node; > > > > + > > > > + if (++cpe_head >= CE_HISTORY_LENGTH) > > > > + cpe_head = 0; > > > > + } > > > > + > > > > + if (!work_scheduled) { > > > > + work_scheduled = 1; > > > > + schedule_work(&cpe_enable_work); > > > > > > So you must not schedule cpe_enable_work if it's already in progress. Why? > > > > If there is already a worker thread scheduled, it will process all > > the addresses on the queue, including new entries. So all ce_setup_migrate() > > needs to do is add the new entry to the queue. The CPE interrupt can come in faster > > than the worker thread can migrate the pages. Scheduling another worker > > thread on each CPE interrupt when there is already one scheduled/running > > would be overkill. > > Okay. Maybe a kthread would be cleaner here then (which sleeps when the > buffer is empty)? I didn't notice any locking for cpe_paddr and cpe_node. > Why is that? Do you mean a lock so that cpe_paddr & cpe_node are updated atomicly? The hole being the new page is allocated on a different node than the old page. -- Russ Anderson, OS RAS/Partitioning Project Lead SGI - Silicon Graphics Inc rja@sgi.com