Re: [PATCH 1/2] sched: Optimize build_sched_domains() for savingfirst SD node for a cpu
From: Peter Zijlstra
Date: Wed Jun 05 2013 - 07:04:50 EST
On Wed, Jun 05, 2013 at 10:37:29AM +0530, Viresh Kumar wrote:
> On 5 June 2013 10:12, Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx> wrote:
> > Hi, Viresh
> >
> > On 06/04/2013 07:20 PM, Viresh Kumar wrote:
> > [snip]
> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> >> index 58453b8..638f6cb 100644
> >> --- a/kernel/sched/core.c
> >> +++ b/kernel/sched/core.c
> >> @@ -6533,16 +6533,13 @@ static int build_sched_domains(const struct cpumask *cpu_map,
> >> sd = NULL;
> >> for (tl = sched_domain_topology; tl->init; tl++) {
> >> sd = build_sched_domain(tl, &d, cpu_map, attr, sd, i);
> >> + if (!*per_cpu_ptr(d.sd, i))
> >
> > What about:
> > if (tl == sched_domain_topology)
> >
> > It cost less than per_cpu_ptr(), isn't it?
>
> How can I miss it.. Obviously its better :)
>
> See if below one looks better (Attached too in case gmail screws up
> my mail)..
>
> --------x-------------x------------------
>
> From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Date: Tue, 4 Jun 2013 15:41:15 +0530
> Subject: [PATCH] sched: Optimize build_sched_domains() for saving first SD
> node for a cpu
>
> We are saving first scheduling domain for a cpu in build_sched_domains() by
> iterating over the nested sd->child list. We don't actually need to do it this
> way.
>
> tl will be equal to sched_domain_topology for the first iteration and so we can
> set *per_cpu_ptr(d.sd, i) based on that. So, save pointer to first SD while
> running the iteration loop over tl's.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> kernel/sched/core.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 58453b8..08a27be 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6533,16 +6533,13 @@ static int build_sched_domains(const struct
> cpumask *cpu_map,
Applying patch
patches/viresh_kumar-_patch__sched-optimize_build_sched_domains_for_saving_first_sd.patch
patching file kernel/sched/core.c
patch: **** malformed patch at line 56: cpumask *cpu_map,
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