netdev - Re: [PATCH] sunrpc: use better NUMA affinities

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Message-Id: <15F25127-70B3-4B42-86DA-E73629C4FE2B@fastmail.fm>
Date:	Sat, 30 Jul 2011 06:24:09 +1000
From:	Greg Banks <gnb@...tmail.fm>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, NeilBrown <neilb@...e.de>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] sunrpc: use better NUMA affinities



Sent from my iPhone

On 30/07/2011, at 2:45, "J. Bruce Fields" <bfields@...ldses.org> wrote:

> On Fri, Jul 29, 2011 at 04:53:21PM +1000, Greg Banks wrote:
>> On 29/07/11 16:30, Eric Dumazet wrote:
>>> Le vendredi 29 juillet 2011 à 16:05 +1000, Greg Banks a écrit :
>>>> 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"?

If you like.

>
>> [...] 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?
>

Relying on global policy was easy but not a great idea, I prefer  
Eric's approach of doing it explicitly.

Greg.
>>
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