From the Solaris 10 kmem_alloc(9F) man page:
The kmem_alloc() function allocates size bytes of kernel
memory and returns a pointer to the allocated memory. The
allocated memory is at least double-word aligned, so it can
hold any C data structure. No greater alignment can be
assumed. flag determines whether the caller can sleep for
memory. KM_SLEEP allocations may sleep but are guaranteed to
succeed. KM_NOSLEEP allocations are guaranteed not to sleep
but may fail (return NULL) if no memory is currently avail-
able. The initial contents of memory allocated using
kmem_alloc() are random garbage.
I have been informed by Oracle internal sources that kmem_alloc(KM_NOSLEEP) can indeed sleep. There apparently is a blocking mutex in the slab allocator refill operation that can be taken even when KM_NOSLEEP is indicated.
Can anybody with Solaris 10 VM internals knowledge shed some more light on this? It's counterintuitive to say the least. Is there any way to allocate kernel memory in Solaris without blocking? Do I really have to write my own memory allocator to work around this deficiency?
Thanks for any help you can provide.