From: Michal Hocko <mhocko@suse.cz>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
Jack Steiner <steiner@sgi.com>,
Lee Schermerhorn <lee.schermerhorn@hp.com>,
Christoph Lameter <cl@linux-foundation.org>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Paul Menage <menage@google.com>, Robin Holt <holt@sgi.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org
Subject: Re: [PATCH incremental] cpusets: initialize spread rotor lazily
Date: Mon, 18 Apr 2011 23:29:16 +0200 [thread overview]
Message-ID: <20110418212915.GA17376@tiehlicka.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.00.1104181316110.31186@chino.kir.corp.google.com>
On Mon 18-04-11 13:19:09, David Rientjes wrote:
> On Mon, 18 Apr 2011, Michal Hocko wrote:
[...]
> > > Andrew could easily drop the earlier version and merge this v2, but I'm
> > > asking for selfish reasons:
> >
> > Just out of curiosity. What is the reason? Don't want to wait for new mmotm?
> >
>
> Because lazy initialization is another feature on top of the existing
> patch so it should be done incrementally instead of proposing an entirely
> new patch which is already mostly in -mm.
ok, makes sense
> >
> > [Here is the follow-up patch based on top of
> > http://userweb.kernel.org/~akpm/mmotm/broken-out/cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch]
> > ---
> > From: Michal Hocko <mhocko@suse.cz>
> > Subject: cpusets: initialize spread mem/slab rotor lazily
> >
[...]
> > Also do not use -1 for unitialized nodes and rather use NUMA_NO_NODE
> > instead.
> >
>
> Don't need to refer to a previous version that used -1 since it will never
> be committed and nobody will know what you're talking about in the git
> log.
removed
[...]
> > int cpuset_mem_spread_node(void)
> > {
> > + if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
> > + current->cpuset_mem_spread_rotor =
> > + node_random(¤t->mems_allowed);
> > +
> > return cpuset_spread_node(¤t->cpuset_mem_spread_rotor);
> > }
> >
> > int cpuset_slab_spread_node(void)
> > {
> > + if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
> > + current->cpuset_slab_spread_rotor
> > + = node_random(¤t->mems_allowed);
> > +
>
> So one function has the `=' on the line with the assignment (preferred)
> and the other has it on the new value?
fixed
Thanks! Updated patch bellow.
Changes from v3:
- code style fix
Changes from v2:
- use NUMA_NO_NODE rather than hardcoded -1
- make the patch incremental to the original one because that one is in
-mm tree already.
Changes from v1:
- initialize cpuset_{mem,slab}_spread_rotor lazily}
---
From: Michal Hocko <mhocko@suse.cz>
Subject: cpusets: initialize spread mem/slab rotor lazily
Kosaki Motohiro raised a concern that copy_process is hot path and we do
not want to initialize cpuset_{mem,slab}_spread_rotor if they are not
used most of the time.
I think that we should rather initialize it lazily when rotors are used
for the first time.
This will also catch the case when we set up spread mem/slab later.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Index: linus_tree/kernel/cpuset.c
===================================================================
--- linus_tree.orig/kernel/cpuset.c 2011-04-18 10:33:15.000000000 +0200
+++ linus_tree/kernel/cpuset.c 2011-04-18 23:24:02.000000000 +0200
@@ -2460,11 +2460,19 @@ static int cpuset_spread_node(int *rotor
int cpuset_mem_spread_node(void)
{
+ if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
+ current->cpuset_mem_spread_rotor =
+ node_random(¤t->mems_allowed);
+
return cpuset_spread_node(¤t->cpuset_mem_spread_rotor);
}
int cpuset_slab_spread_node(void)
{
+ if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
+ current->cpuset_slab_spread_rotor =
+ node_random(¤t->mems_allowed);
+
return cpuset_spread_node(¤t->cpuset_slab_spread_rotor);
}
Index: linus_tree/kernel/fork.c
===================================================================
--- linus_tree.orig/kernel/fork.c 2011-04-18 10:33:15.000000000 +0200
+++ linus_tree/kernel/fork.c 2011-04-18 10:33:56.000000000 +0200
@@ -1126,8 +1126,8 @@ static struct task_struct *copy_process(
mpol_fix_fork_child_flag(p);
#endif
#ifdef CONFIG_CPUSETS
- p->cpuset_mem_spread_rotor = node_random(&p->mems_allowed);
- p->cpuset_slab_spread_rotor = node_random(&p->mems_allowed);
+ p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
+ p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
p->irq_events = 0;
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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next prev parent reply other threads:[~2011-04-18 21:29 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20110414065146.GA19685@tiehlicka.suse.cz>
[not found] ` <20110414160145.0830.A69D9226@jp.fujitsu.com>
[not found] ` <20110415161831.12F8.A69D9226@jp.fujitsu.com>
2011-04-15 8:20 ` [PATCH v2] cpusets: randomize node rotor used in cpuset_mem_spread_node() Michal Hocko
2011-04-15 8:29 ` KOSAKI Motohiro
2011-04-15 8:31 ` Michal Hocko
2011-04-15 23:42 ` David Rientjes
2011-04-18 8:42 ` [PATCH incremental] cpusets: initialize spread rotor lazily Michal Hocko
2011-04-18 20:19 ` David Rientjes
2011-04-18 21:29 ` Michal Hocko [this message]
2011-04-19 1:15 ` David Rientjes
2011-05-26 22:33 ` [PATCH v2] cpusets: randomize node rotor used in cpuset_mem_spread_node() Andrew Morton
2011-05-27 12:47 ` Michal Hocko
2011-05-27 19:07 ` David Rientjes
2011-05-27 23:17 ` Michal Hocko
2011-05-27 23:27 ` David Rientjes
2011-05-27 23:40 ` Michal Hocko
2011-05-27 21:20 ` Andrew Morton
2011-05-27 23:17 ` Michal Hocko
2011-05-27 23:30 ` David Rientjes
2011-05-27 23:38 ` Michal Hocko
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