diff options
author | Rik van Riel <riel@redhat.com> | 2013-10-07 14:29:39 +0400 |
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committer | Ingo Molnar <mingo@kernel.org> | 2013-10-09 16:48:21 +0400 |
commit | de1c9ce6f07fec0381a39a9d0b379ea35aa1167f (patch) | |
tree | d96bf1a2b25dfa84d3fe5f6fe00fb780800e3ef3 /mm | |
parent | 1e3646ffc64b232cb14a5ef01d7b98997c1b73f9 (diff) | |
download | linux-de1c9ce6f07fec0381a39a9d0b379ea35aa1167f.tar.xz |
sched/numa: Skip some page migrations after a shared fault
Shared faults can lead to lots of unnecessary page migrations,
slowing down the system, and causing private faults to hit the
per-pgdat migration ratelimit.
This patch adds sysctl numa_balancing_migrate_deferred, which specifies
how many shared page migrations to skip unconditionally, after each page
migration that is skipped because it is a shared fault.
This reduces the number of page migrations back and forth in
shared fault situations. It also gives a strong preference to
the tasks that are already running where most of the memory is,
and to moving the other tasks to near the memory.
Testing this with a much higher scan rate than the default
still seems to result in fewer page migrations than before.
Memory seems to be somewhat better consolidated than previously,
with multi-instance specjbb runs on a 4 node system.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-62-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/mempolicy.c | 48 |
1 files changed, 47 insertions, 1 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 2929c24c22b7..71cb253368cb 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2301,6 +2301,35 @@ 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 * @@ -2402,7 +2431,24 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long * relation. */ last_cpupid = page_cpupid_xchg_last(page, this_cpupid); - if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != thisnid) + 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; } |