From: David Rientjes <rientjes@google.com>
To: Christoph Lameter <cl@linux.com>, Eric Dumazet <edumazet@google.com>
Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Anton Blanchard <anton@samba.org>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
Jan Kara <jack@suse.cz>, Thomas Gleixner <tglx@linutronix.de>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
linux-mm@kvack.org, Wanpeng Li <liwanp@linux.vnet.ibm.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Ben Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] kthread: ensure locality of task_struct allocations
Date: Wed, 29 Jan 2014 16:27:22 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.02.1401291622550.22974@chino.kir.corp.google.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1401290957350.23856@nuc>
On Wed, 29 Jan 2014, Christoph Lameter wrote:
> > > diff --git a/kernel/kthread.c b/kernel/kthread.c
> > > index b5ae3ee..8573e4e 100644
> > > --- a/kernel/kthread.c
> > > +++ b/kernel/kthread.c
> > > @@ -217,7 +217,7 @@ int tsk_fork_get_node(struct task_struct *tsk)
> > > if (tsk == kthreadd_task)
> > > return tsk->pref_node_fork;
> > > #endif
> > > - return numa_node_id();
> > > + return numa_mem_id();
> >
> > I'm wondering why return NUMA_NO_NODE wouldn't have the same effect and
> > prefer the local node?
> >
>
> The idea here seems to be that the allocation may occur from a cpu that is
> different from where the process will run later on.
>
Yeah, that makes sense for kthreadd, but I'm wondering why we have to
return numa_mem_id() rather than just NUMA_NO_NODE. Sorry for not being
specific about doing s/numa_mem_id/NUMA_NO_NODE/ here.
That should just turn kmem_cache_alloc_node() into kmem_cache_alloc() and
alloc_pages_node() into alloc_pages() for the allocators that use this
return value, task_struct and thread_info. If that's not allocating local
memory, if possible, and numa_mem_id() magically does, then there's a
problem.
Eric, did you try this when writing 207205a2ba26 ("kthread: NUMA aware
kthread_create_on_node()") or was it always numa_node_id() from the
beginning?
next prev parent reply other threads:[~2014-01-30 0:27 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-28 18:38 [PATCH] kthread: ensure locality of task_struct allocations Nishanth Aravamudan
2014-01-29 8:13 ` David Rientjes
2014-01-29 15:58 ` Christoph Lameter
2014-01-30 0:27 ` David Rientjes [this message]
2014-01-30 6:14 ` Eric Dumazet
2014-01-30 22:47 ` David Rientjes
2014-01-30 23:08 ` Nishanth Aravamudan
2014-01-30 23:31 ` David Rientjes
2014-01-31 15:14 ` Christoph Lameter
2014-01-29 15:57 ` Christoph Lameter
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