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sched/numa, mm: Remove p->numa_migrate_deferred

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Excessive migration of pages can hurt the performance of workloads
that span multiple NUMA nodes.  However, it turns out that the
p->numa_migrate_deferred knob is a really big hammer, which does
reduce migration rates, but does not actually help performance.

Now that the second stage of the automatic numa balancing code
has stabilized, it is time to replace the simplistic migration
deferral code with something smarter.

Signed-off-by: Rik van Riel <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Chegu Vinod <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Rik van Riel 2014-01-27 17:03:40 -05:00 • committed by Ingo Molnar
commit 52bf84aa20
5 changed files with 1 additions and 70 deletions
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45
mm/mempolicy.c
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@ -2304,35 +2304,6 @@ static void sp_free(struct sp_node *n)
kmem_cache_free(sn_cache, n);
}
#ifdef CONFIG_NUMA_BALANCING
static bool numa_migrate_deferred(struct task_struct *p, int last_cpupid)
{
/* Never defer a private fault */
if (cpupid_match_pid(p, last_cpupid))
return false;
if (p->numa_migrate_deferred) {
p->numa_migrate_deferred--;
return true;
}
return false;
}
static inline void defer_numa_migrate(struct task_struct *p)
{
p->numa_migrate_deferred = sysctl_numa_balancing_migrate_deferred;
}
#else
static inline bool numa_migrate_deferred(struct task_struct *p, int last_cpupid)
{
return false;
}
static inline void defer_numa_migrate(struct task_struct *p)
{
}
#endif /* CONFIG_NUMA_BALANCING */
/**
* mpol_misplaced - check whether current page node is valid in policy
*
@ -2435,24 +2406,8 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
*/
last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != thisnid) {
/* See sysctl_numa_balancing_migrate_deferred comment */
if (!cpupid_match_pid(current, last_cpupid))
defer_numa_migrate(current);
goto out;
}
/*
* The quadratic filter above reduces extraneous migration
* of shared pages somewhat. This code reduces it even more,
* reducing the overhead of page migrations of shared pages.
* This makes workloads with shared pages rely more on
* "move task near its memory", and less on "move memory
* towards its task", which is exactly what we want.
*/
if (numa_migrate_deferred(current, last_cpupid))
goto out;
}
if (curnid != polnid)