[PATCH] sched: remove SMT nice

Remove the SMT-nice feature which idles sibling cpus on SMT cpus to
facilitiate nice working properly where cpu power is shared.  The idling of
cpus in the presence of runnable tasks is considered too fragile, easy to
break with outside code, and the complexity of managing this system if an
architecture comes along with many logical cores sharing cpu power will be
unworkable.

Remove the associated per_cpu_gain variable in sched_domains used only by
this code.

Also:

  The reason is that with dynticks enabled, this code breaks without yet
  further tweaks so dynticks brought on the rapid demise of this code.  So
  either we tweak this code or kill it off entirely.  It was Ingo's preference
  to kill it off.  Either way this needs to happen for 2.6.21 since dynticks
  has gone in.

Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 0 insertions, 5 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6f7c9a4d80e5..49fe2997a016 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -684,7 +684,6 @@ struct sched_domain {
         unsigned int imbalance_pct;     /* No balance until over watermark */
         unsigned long long cache_hot_time; /* Task considered cache hot (ns) */
         unsigned int cache_nice_tries;  /* Leave cache hot tasks for # tries */
-        unsigned int per_cpu_gain;      /* CPU % gained by adding domain cpus */
         unsigned int busy_idx;
         unsigned int idle_idx;
         unsigned int newidle_idx;
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 6c5a6e6e813b..a9d1f049cc15 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -96,7 +96,6 @@
         .busy_factor            = 64,                   \
         .imbalance_pct          = 110,                  \
         .cache_nice_tries       = 0,                    \
-        .per_cpu_gain           = 25,                   \
         .busy_idx               = 0,                    \
         .idle_idx               = 0,                    \
         .newidle_idx            = 1,                    \
@@ -128,7 +127,6 @@
         .busy_factor            = 64,                   \
         .imbalance_pct          = 125,                  \
         .cache_nice_tries       = 1,                    \
-        .per_cpu_gain           = 100,                  \
         .busy_idx               = 2,                    \
         .idle_idx               = 1,                    \
         .newidle_idx            = 2,                    \
@@ -159,7 +157,6 @@
         .busy_factor            = 64,                   \
         .imbalance_pct          = 125,                  \
         .cache_nice_tries       = 1,                    \
-        .per_cpu_gain           = 100,                  \
         .busy_idx               = 2,                    \
         .idle_idx               = 1,                    \
         .newidle_idx            = 2,                    \
@@ -193,7 +190,6 @@
         .newidle_idx            = 0, /* unused */       \
         .wake_idx               = 0, /* unused */       \
         .forkexec_idx           = 0, /* unused */       \
-        .per_cpu_gain           = 100,                  \
         .flags                  = SD_LOAD_BALANCE       \
                                 | SD_SERIALIZE, \
         .last_balance           = jiffies,              \