lkml.org 
[lkml]   [2011]   [Apr]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH incremental] cpusets: initialize spread rotor lazily
On Fri 15-04-11 16:42:13, David Rientjes wrote:
> On Fri, 15 Apr 2011, Michal Hocko wrote:
>
> > You are right. I was thinking about lazy approach and initialize those
> > values when they are used for the first time. What about the patch
> > below?
> >
> > Change from v1:
> > - initialize cpuset_{mem,slab}_spread_rotor lazily
> >
>
> The difference between this v2 patch and what is already in the -mm tree
> (http://userweb.kernel.org/~akpm/mmotm/broken-out/cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch)
> is the lazy initialization by adding cpuset_{mem,slab}_spread_node()?

Yes.

> It'd probably be better to just make an incremental patch on top of
> mmotm-2011-04-14-15-08 with a new changelog and then propose with with
> your list of reviewed-by lines.

Sure, no problems. Maybe it will be easier for Andrew as well.

>
> 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?

> please use NUMA_NO_NODE instead of -1.

Good idea. I have updated the patch.

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}
[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
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 intialize it lazily when rotors are used
for the first time.
This will also catch the case when we set up spread mem/slab later.

Also do not use -1 for unitialized nodes and rather use NUMA_NO_NODE
instead.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
cpuset.c | 8 ++++++++
fork.c | 4 ++--
2 files changed, 10 insertions(+), 2 deletions(-)
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 10:33:56.000000000 +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(&current->mems_allowed);
+
return cpuset_spread_node(&current->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(&current->mems_allowed);
+
return cpuset_spread_node(&current->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

\
 
 \ /
  Last update: 2011-04-18 10:45    [from the cache]
©2003-2011 Jasper Spaans