Messages in this thread | | | Date | Wed, 26 Apr 2006 15:42:03 +0200 | From | Jes Sorensen <> | Subject | Re: [PATCH] change gen_pool allocator to not touch managed memory |
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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
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