[lkml]   [2012]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 1/5] staging: zsmalloc: zsmalloc memory allocation library
On 02/06/2012 09:26 AM, Seth Jennings wrote:
> On 01/26/2012 01:12 PM, Dave Hansen wrote:
>> void *kmap_atomic_prot(struct page *page, pgprot_t prot)
>> {
>> ...
>> type = kmap_atomic_idx_push();
>> idx = type + KM_TYPE_NR*smp_processor_id();
>> vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
>> I think if you do a get_cpu()/put_cpu() or just a preempt_disable()
>> across the operations you'll be guaranteed to get two contiguous addresses.
> I'm not quite following here. kmap_atomic() only does this for highmem pages.
> For normal pages (all pages for 64-bit), it doesn't do any mapping at all. It
> just returns the virtual address of the page since it is in the kernel's address
> space.
> For this design, the pages _must_ be mapped, even if the pages are directly
> reachable in the address space, because they must be virtually contiguous.

I guess you could use vmap() for that. It's just going to be slower
than kmap_atomic(). I'm really not sure it's worth all the trouble to
avoid order-1 allocations, though.

 \ /
  Last update: 2012-02-08 17:45    [W:0.056 / U:1.812 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site