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sched/numa: Remove numa_has_capacity() 

task_numa_find_cpu() helps to find the CPU to swap/move the task to.
It's guarded by numa_has_capacity(). However node not having capacity
shouldn't deter a task swapping if it helps NUMA placement.

Further load_too_imbalanced(), which evaluates possibilities of move/swap,
provides similar checks as numa_has_capacity.

Hence remove numa_has_capacity() to enhance possibilities of task
swapping even if load is imbalanced.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
16    25657.9     25804.1     0.569
1     74435       73413       -1.37

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1529514181-9842-13-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Srikar Dronamraju 2018-06-20 22:32:53 +05:30 committed by Ingo Molnar
parent 0ad4e3dfe6
commit 2d4056fafa
1 changed files with 3 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
kernel/sched/fair.c
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@ -1456,7 +1456,6 @@ struct numa_stats {
unsigned long compute_capacity; unsigned long compute_capacity;
unsigned int nr_running; unsigned int nr_running;
int has_free_capacity;
}; };
/* /*
@ -1483,8 +1482,7 @@ static void update_numa_stats(struct numa_stats *ns, int nid)
* the @ns structure is NULL'ed and task_numa_compare() will * the @ns structure is NULL'ed and task_numa_compare() will
* not find this node attractive. * not find this node attractive.
* *
* We'll either bail at !has_free_capacity, or we'll detect a huge * We'll detect a huge imbalance and bail there.
* imbalance and bail there.
*/ */
if (!cpus) if (!cpus)
return; return;
@ -1495,7 +1493,6 @@ static void update_numa_stats(struct numa_stats *ns, int nid)
capacity = min_t(unsigned, capacity, capacity = min_t(unsigned, capacity,
DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE)); DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
ns->has_free_capacity = (ns->nr_running < capacity);
} }
struct task_numa_env { struct task_numa_env {
@ -1698,31 +1695,6 @@ static void task_numa_find_cpu(struct task_numa_env *env,
} }
} }
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
struct numa_stats *src = &env->src_stats;
struct numa_stats *dst = &env->dst_stats;
if (src->has_free_capacity && !dst->has_free_capacity)
return false;
/*
* Only consider a task move if the source has a higher load
* than the destination, corrected for CPU capacity on each node.
*
* src->load dst->load
* --------------------- vs ---------------------
* src->compute_capacity dst->compute_capacity
*/
if (src->load * dst->compute_capacity * env->imbalance_pct >
dst->load * src->compute_capacity * 100)
return true;
return false;
}
static int task_numa_migrate(struct task_struct *p) static int task_numa_migrate(struct task_struct *p)
{ {
struct task_numa_env env = { struct task_numa_env env = {
@ -1777,8 +1749,7 @@ static int task_numa_migrate(struct task_struct *p)
update_numa_stats(&env.dst_stats, env.dst_nid); update_numa_stats(&env.dst_stats, env.dst_nid);
/* Try to find a spot on the preferred nid. */ /* Try to find a spot on the preferred nid. */
if (numa_has_capacity(&env)) task_numa_find_cpu(&env, taskimp, groupimp);
task_numa_find_cpu(&env, taskimp, groupimp);
/* /*
* Look at other nodes in these cases: * Look at other nodes in these cases:
@ -1808,8 +1779,7 @@ static int task_numa_migrate(struct task_struct *p)
env.dist = dist; env.dist = dist;
env.dst_nid = nid; env.dst_nid = nid;
update_numa_stats(&env.dst_stats, env.dst_nid); update_numa_stats(&env.dst_stats, env.dst_nid);
if (numa_has_capacity(&env)) task_numa_find_cpu(&env, taskimp, groupimp);
task_numa_find_cpu(&env, taskimp, groupimp);
} }
} }