On Fri, Jul 29, 2011 at 04:53:21PM +1000, Greg Banks wrote:

On 29/07/11 16:30, Eric Dumazet wrote:

quoted

Le vendredi 29 juillet 2011 à 16:05 +1000, Greg Banks a écrit :

quoted

On 29/07/11 15:32, NeilBrown wrote:

I seem to remember coming to the conclusion that Jeff eventually
addressed this problem...am I misremembering or did something regress?

Currently, all nfsd kthreads use memory for their kernel stack and
various initial data from a _single_ node, even if you use
sunrpc.pool_mode=pernode  (or percpu)

That's just plain broken and I'm very pleased to see you fix it.

Should I take that as a "Reviewed-by"?

I was just surprised that it was still broken and wondering how that
happened.  Looking at ToT I see that because I dropped the ball in
2008, Jeff's patches didn't address the problem.  In ToT
svc_pool_map_set_cpumask() is called *after* kthread_create() and
applies to the child thread, *after* it's stack has been allocated
on the wrong node.  In the working SGI code,
svc_pool_map_set_cpumask() is called by the parent node on itself
*before* calling kernel_thread() or doing any of the data structure
allocations, thus ensuring that everything gets allocated using the
default memory allocation policy, which on SGI NFS servers was
globally tuned to be "node-local".

OK, so would it be enough to just move the svc_pool_map_set_cpumask()
back a few lines, or do we want Eric's approach, in order to have
something that will work better with other memory allocation policies?

--b.

quoted

With my patch, we make sure each thread gets its stack from its local
node.

Check commit 94dcf29a11b3d20a (kthread: use kthread_create_on_node()) to
see how this strategy already was adopted for ksoftirqd, kworker,
migration, and pktgend kthreads.

Ah, I see.  It's unfortunate that the kthread_create() API ends up
being passed a CPU number but that's only used to format the name
and not for sensible things :(

-- 
Greg.

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