On 18.12.2012 06:40, Oleksandr Tymoshenko wrote:
On 2012-12-08, at 1:21 PM, Alan Cox <a...@rice.edu> wrote:
On 12/08/2012 14:32, Andre Oppermann wrote:
.. skipped ..
The trouble seems to come from NSFBUFS which is (512 + maxusers * 16)
resulting in a kernel map of (512 + 400 * 16) * PAGE_SIZE = 27MB. This
seem to be pushing it with the smaller ARM kmap layout.
Does it boot and run when you set the tunable kern.ipc.nsfbufs=3500?
ARM does have a direct map mode as well which doesn't require the
allocation
of sfbufs. I'm not sure which other problems that approach has.
Only a few (3?) platforms use it. It reduces the size of the user
address space, and translation between physical addresses and direct map
addresses is not computationally trivial as it is on other
architectures, e.g., amd64, ia64. However, it does try to use large
page mappings.
Hopefully alc@ (added to cc) can answer that and also why the kmap of
27MB
manages to wrench the ARM kernel.
Arm does not define caps on either the buffer map size (param.h) or the
kmem map size (vmparam.h). It would probably make sense to copy these
definitions from i386.
Adding caps didn't help. I did some digging and found out that although address
range
0xc0000000 .. 0xffffffff is indeed valid for ARM in general actual KVA space
varies for
each specific hardware platform. This "real" KVA is defined by <virtual_avail,
virtual_end>
pair and ifI use them instead of <VM_MIN_KERNEL_ADDRESS, VM_MAX_KERNEL_ADDRESS>
in init_param2 function my pandaboard successfully boots. Since former pair is
used for defining
kernel_map boundaries I believe it should be used for auto tuning as well.
OK. Thank you for debugging this on ARM. I'll adjust the auto-tuning
code accordingly.
--
Andre
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