[RFC][CFT] GEOM direct dispatch and fine-grained CAM locking

[Nathan Whitehorn]

On 09/04/13 08:20, Ryan Stone wrote:
> On Wed, Sep 4, 2013 at 8:45 AM, Nathan Whitehorn <nwhitehorn at freebsd.org> wrote:
>> Could you describe what this macro is supposed to do so that we can do the
>> porting work?
>> -Nathan
> #define GET_STACK_USAGE(total, used)
>
> GET_STACK_USAGE sets the variable passed in total to the total amount
> of stack space available to the current thread.  used is set to the
> amount of stack space currently used (this does not have to have
> byte-precision).  Netgraph uses this to decide when to stop recursing
> and instead defer to a work queue (to prevent stack overflow).  I
> presume that Alexander is using it in a similar way.  It looks like
> the amd64 version could be ported to other architectures quite easily
> if you were to account for stacks that grow up and stacks that grow
> down:
>
> http://svnweb.freebsd.org/base/head/sys/amd64/include/proc.h?revision=233291&view=markup
>
> /* Get the current kernel thread stack usage. */
> #define GET_STACK_USAGE(total, used) do {                \
>      struct thread    *td = curthread;                \
>      (total) = td->td_kstack_pages * PAGE_SIZE;            \
>      (used) = (char *)td->td_kstack +                \
>          td->td_kstack_pages * PAGE_SIZE -                \
>          (char *)&td;                        \
> } while (0)
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I think that should be MI for us anyway. I'm not aware of any 
architectures FreeBSD supports with stacks that grow up. I'll give it a 
test on PPC.
-Nathan