On 01.02.2013 18:52, Alan Cox wrote:
On 02/01/2013 04:26, Andre Oppermann wrote:
Author: andre
Date: Fri Feb 1 10:26:31 2013
New Revision: 246204
URL: http://svnweb.freebsd.org/changeset/base/246204
Log:
Add VM_KMEM_SIZE_SCALE parameter set to 2 (50%) for all ARM platforms.
VM_KMEM_SIZE_SCALE specifies which fraction of the available physical
memory, after deduction of the kernel itself and other early statically
allocated memory, can be used for the kmem_map. The kmem_map provides
for all UMA/malloc allocations in KVM space.
Not always. Off the top of my head, two things immediately come to
mind: 9KB and 16KB jumbo frames come from the kernel map, because we
allocate physically contiguous memory for them, and some swap metadata
also comes from the kernel map.
I'd love to remove jumbo clusters that are larger than PAGE_SIZE. The
hard need of s/g challenged network cards is gone. All contemporary
networks can deliver a jumbo frame into a PAGE_SIZE'd mbuf cluster chains.
Some can even split off the headers into a separate mbuf.
A quick search for kernel_map allocations didn't show many other direct
users of the kernel_map. The XEN net and blk backends do make use of it.
Other users have their own submaps: exec_map, pipe_map, buffer_map and
pager_map.
Yes, all "ordinary" heap allocations come from the kmem map, but a
number of things that are special for one reason or another don't.
--
Andre
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