From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jes Sorensen Date: Wed, 26 Apr 2006 13:42:03 +0000 Subject: Re: [PATCH] change gen_pool allocator to not touch managed memory Message-Id: <444F78AB.6030803@sgi.com> List-Id: References: <444D1A7E.mailx85W11DZZU@aqua.americas.sgi.com> <20060424181626.09966912.akpm@osdl.org> <20060425155051.GA19248@sgi.com> <444F3990.5030100@sgi.com> <20060426132803.GA30360@sgi.com> In-Reply-To: <20060426132803.GA30360@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dean Nelson Cc: akpm@osdl.org, tony.luck@intel.com, avolkov@varma-el.com, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, paulus@samba.org, holt@sgi.com Dean Nelson wrote: > On Wed, Apr 26, 2006 at 11:12:48AM +0200, Jes Sorensen wrote: >> Dean Nelson wrote: >>> + if (nbytes > PAGE_SIZE) { >>> + chunk = vmalloc_node(nbytes, nid); >>> + } else { >>> + chunk = kmalloc_node(nbytes, GFP_KERNEL, nid); >>> + } >> Any patch that adds vmalloc() calls to code always makes the little >> hairs on the back of my neck stand up. Any chance we could get away with >> alloc_pages_node() for this? > > Is it the mapping of the pages that bothers you? If using alloc_pages_node() > is the preferred way, I certainly can make the change. But if I do there is > a greater potential that we may have to return failure to the caller of > gen_pool_add(), that is if we can't get the necessary number of contiguous > pages. Now granted the likelyhood that anyone would require more than a > page for a bitmap is very very small. I'd say the vast majority of callers > will end up using kmalloc_node(). I can go either way, just let me know > whether I should make the change or not. vmalloc mappings are $$$ on many archs so they should be avoided if in any way possible. Also, kmalloc can handle more than just a page, and it might be better to just use that here rather than alloc_pages actually since I presume there is nothing preventing the bitmap sharing pages with other data. In this case I think adding the vmalloc call is overkill, I would simply make it call kmalloc_node() unconditionally for all sizes and let it fail if that situation occurs, given how unlikely it is. >>> Index: linux-2.6/arch/ia64/sn/kernel/sn2/cache.c >>> =================================>>> --- linux-2.6.orig/arch/ia64/sn/kernel/sn2/cache.c 2006-04-24 12:25:36.234717101 -0500 >>> +++ linux-2.6/arch/ia64/sn/kernel/sn2/cache.c 2006-04-24 12:27:56.012899026 -0500 >> This part we should maybe do in a seperate patch? It seems valid on it's >> own? > > I thought of this, but if this patch were separated out then the remaining > patch would be dependent on it since the uncached allocator is being > changed to call sn_flush_all_caches() with an uncached address. > It certainly could be done, but is it worth the effort? Let me know > how I should proceed with this. I would expect this part of the patch to be able to go in as is, straight away so I don't think it should be a problem. It's not a big deal whether we do it one way or another to me. Cheers, Jes