Use of contiguous physical memory in cxgbe driver

[Adrian Chadd]

On 11 February 2014 10:48, John Baldwin <jhb at freebsd.org> wrote:
> On Thursday, January 23, 2014 2:32:51 am Adrian Chadd wrote:
>> It's about time we taught the physmem allocator to be more conducive
>> to physically contiguous allocations.
>>
>> A server with gigabytes of memory should be able to keep a couple tens
>> of megabytes of 64k sized allocation chunks around for exactly this.
>
> Alan Cox already taught the physmem allocator to do this for superpages.
> However, this change was part of the superpages changes, so you can't count
> experiences from machines older than about 7.2 when evaluating the
> effectiveness of the new allocator.

the problem is that we don't have pressure to _not_ fragment the
physical memory from the allocator, so all of the memory ends up
getting very fragmented versy quickly.

the physmem superpage stuff stops being viable after a short while of
say, "pound lots of packets around from vm objects" workload, because
suddenly we end up chewing through all of physical memory with pages
extremely quickly.



-a