linux-kernel - Re: High priority tasks break SMP balancer?

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Message-ID: <b647ffbd0711201347tedf7ac0sc6476118353feab3@mail.gmail.com>
Date:	Tue, 20 Nov 2007 22:47:52 +0100
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"Micah Dowty" <micah@...are.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Christoph Lameter" <clameter@....com>,
	"Kyle Moffett" <mrmacman_g4@....com>,
	"Cyrus Massoumi" <cyrusm@....net>,
	"LKML Kernel" <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...l.org>, "Mike Galbraith" <efault@....de>,
	"Paul Menage" <menage@...gle.com>,
	"Peter Williams" <pwil3058@...pond.net.au>
Subject: Re: High priority tasks break SMP balancer?

On 20/11/2007, Micah Dowty <micah@...are.com> wrote:
> On Tue, Nov 20, 2007 at 06:57:55AM +0100, Ingo Molnar wrote:
> >
> > * Micah Dowty <micah@...are.com> wrote:
> >
> > > > this one is being triggered whenever a cpu becomes idle (schedule()
> > > > --> idle_balance() --> load_balance_newidle()).
> > > >
> > > > (this flag is a bit #1 == 2)
> > > >
> > > > cat /proc/sys/kernel/sched_domain/cpu0/domain0/flags
> > >
> > > Hmm. I don't have this file on my system:
> > >
> > > root@...ah-64:/proc/sys/kernel/sched_domain/cpu0/domain0# ls
> > > busy_factor  busy_idx  forkexec_idx  idle_idx  imbalance_pct  max_interval  min_interval  newidle_idx  wake_idx
> > > root@...ah-64:/proc/sys/kernel/sched_domain/cpu0/domain0# uname -a
> > > Linux micah-64 2.6.23.1 #1 SMP Fri Nov 2 12:25:47 PDT 2007 x86_64 GNU/Linux
> > >
> > > Is there a config option I'm missing?
> >
> > yes, CONFIG_SCHED_DEBUG.
>
> I have that one. I even posted the /proc/sched_debug output :)

ah ok, try applying this patch on top of 2.6.23.1.

btw., what's your system? If I recall right, SD_BALANCE_NEWIDLE is on
by default for all configs, except for NUMA nodes.

(attached a white-space non-damaged version)

---

--- kernel/sched.c-old  2007-11-20 22:33:22.000000000 +0100
+++ kernel/sched.c      2007-11-20 22:37:07.000000000 +0100
@@ -5306,7 +5306,7 @@ set_table_entry(struct ctl_table *entry,
 static struct ctl_table *
 sd_alloc_ctl_domain_table(struct sched_domain *sd)
 {
-       struct ctl_table *table = sd_alloc_ctl_entry(14);
+       struct ctl_table *table = sd_alloc_ctl_entry(12);

        set_table_entry(&table[0], "min_interval", &sd->min_interval,
                sizeof(long), 0644, proc_doulongvec_minmax);
@@ -5326,10 +5326,10 @@ sd_alloc_ctl_domain_table(struct sched_d
                sizeof(int), 0644, proc_dointvec_minmax);
        set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
                sizeof(int), 0644, proc_dointvec_minmax);
-       set_table_entry(&table[10], "cache_nice_tries",
+       set_table_entry(&table[9], "cache_nice_tries",
                &sd->cache_nice_tries,
                sizeof(int), 0644, proc_dointvec_minmax);
-       set_table_entry(&table[12], "flags", &sd->flags,
+       set_table_entry(&table[10], "flags", &sd->flags,
                sizeof(int), 0644, proc_dointvec_minmax);

        return table;

---

>
> --Micah
>
>


-- 
Best regards,
Dmitry Adamushko

View attachment "sd_alloc.patch" of type "text/x-patch" (1033 bytes)