[PATCH] knfsd: provide sunrpc pool_mode module option

Provide a module param "pool_mode" for sunrpc.ko which allows a sysadmin to
choose the mode for mapping NFS thread service pools to CPUs.  Values are:

auto	    choose a mapping mode heuristically
global	    (default, same as the pre-2.6.19 code) a single global pool
percpu	    one pool per CPU
pernode	    one pool per NUMA node

Note that since 2.6.19 the hardcoded behaviour has been "auto", this patch
makes the default "global".

The pool mode can be changed after boot/modprobe using /sys, if the NFS and
lockd services have been shut down.  A useful side effect of this change is to
fix a small memory leak when unloading the module.

Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/kernel-parameters.txt

@@ -1685,6 +1685,22 @@ and is between 256 and 4096 characters. It is defined in the file
 	stifb=		[HW]
 			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
 
+	sunrpc.pool_mode=
+			[NFS]
+			Control how the NFS server code allocates CPUs to
+			service thread pools.  Depending on how many NICs
+			you have and where their interrupts are bound, this
+			option will affect which CPUs will do NFS serving.
+			Note: this parameter cannot be changed while the
+			NFS server is running.
+
+			auto	    the server chooses an appropriate mode
+				    automatically using heuristics
+			global	    a single global pool contains all CPUs
+			percpu	    one pool for each CPU
+			pernode	    one pool for each NUMA node (equivalent
+				    to global on non-NUMA machines)
+
 	swiotlb=	[IA-64] Number of I/O TLB slabs
 
 	switches=	[HW,M68k]