linux-kernel - Re: [PATCH] workqueue: Allocate the unbound pool using local node memory

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Date:	Sat, 10 Oct 2015 09:02:24 +0800
From:	pang.xunlei@....com.cn
To:	"Hillf Danton" <hillf.zj@...baba-inc.com>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"'Xunlei Pang'" <pang.xunlei@...aro.org>,
	"Tejun Heo" <tj@...nel.org>
Subject: Re: [PATCH] workqueue: Allocate the unbound pool using local node memory

Hello,

"Hillf Danton" <hillf.zj@...baba-inc.com> wrote 2015-10-09 PM 06:05:20:
> 
> Re: [PATCH] workqueue: Allocate the unbound pool using local node memory
> 
> > From: Xunlei Pang <pang.xunlei@...aro.org>
> > 
> > Currently, get_unbound_pool() uses kzalloc() to allocate the
> > worker pool. Actually, we can use the right node to do the
> > allocation, achieving local memory access.
> > 
> > This patch selects target node first, and uses kzalloc_node()
> > instead.
> > 
> > Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>
> > ---
> >  kernel/workqueue.c | 26 ++++++++++++++------------
> >  1 file changed, 14 insertions(+), 12 deletions(-)
> > 
> > diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> > index ca71582..96d3747 100644
> > --- a/kernel/workqueue.c
> > +++ b/kernel/workqueue.c
> > @@ -3199,6 +3199,7 @@ static struct worker_pool *get_unbound_pool
> (const struct workqueue_attrs *attrs)
> >     u32 hash = wqattrs_hash(attrs);
> >     struct worker_pool *pool;
> >     int node;
> > +   int target_node = NUMA_NO_NODE;
> > 
> >     lockdep_assert_held(&wq_pool_mutex);
> > 
> > @@ -3210,13 +3211,25 @@ static struct worker_pool 
> *get_unbound_pool(const struct workqueue_attrs *attrs)
> >        }
> >     }
> > 
> > +   /* if cpumask is contained inside a NUMA node, we belong to that 
node */
> > +   if (wq_numa_enabled) {
> > +      for_each_node(node) {
> > +         if (cpumask_subset(attrs->cpumask,
> > +                  wq_numa_possible_cpumask[node])) {
> > +            target_node = node;
> > +            break;
> > +         }
> > +      }
> > +   }
> > +
> >     /* nope, create a new one */
> > -   pool = kzalloc(sizeof(*pool), GFP_KERNEL);
> > +   pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
> 
> What if target_node is short of pages at the moment?

IIRC, the zonelist to be used contains all nodes' zones in order 
(otherwise __GFP_THISNODE is set)with target_node's zones having 
the highest priority, so it should automatically fall back to 
other nodes if target_node is short of pages.

Regards,
-Xunlei

> 
> >     if (!pool || init_worker_pool(pool) < 0)
> >        goto fail;
> > 
> >     lockdep_set_subclass(&pool->lock, 1);   /* see put_pwq() */
> >     copy_workqueue_attrs(pool->attrs, attrs);
> > +   pool->node = target_node;
> > 
> >     /*
> >      * no_numa isn't a worker_pool attribute, always clear it.  See
> > @@ -3224,17 +3237,6 @@ static struct worker_pool *get_unbound_pool
> (const struct workqueue_attrs *attrs)
> >      */
> >     pool->attrs->no_numa = false;
> > 
> > -   /* if cpumask is contained inside a NUMA node, we belong to that 
node */
> > -   if (wq_numa_enabled) {
> > -      for_each_node(node) {
> > -         if (cpumask_subset(pool->attrs->cpumask,
> > -                  wq_numa_possible_cpumask[node])) {
> > -            pool->node = node;
> > -            break;
> > -         }
> > -      }
> > -   }
> > -
> >     if (worker_pool_assign_id(pool) < 0)
> >        goto fail;
> > 
> > --
> > 1.9.1
> 

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