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SubjectRe: [RT LATENCY] 249 microsecond latency caused by slub's unfreeze_partials() code.
On 13-04-01 11:32 AM, Christoph Lameter wrote:

[...]

> @@ -4583,6 +4615,7 @@ static ssize_t min_partial_store(struct
> }
> SLAB_ATTR(min_partial);
>
> +#ifdef CONFIG_CPU_PARTIAL

Above causes build failures when stats are on, because the
name is wrong and hence is never defined, and ....

> static ssize_t cpu_partial_show(struct kmem_cache *s, char *buf)
> {
> return sprintf(buf, "%u\n", s->cpu_partial);
> @@ -4605,6 +4638,7 @@ static ssize_t cpu_partial_store(struct
> return length;
> }
> SLAB_ATTR(cpu_partial);
> +#endif
>
> static ssize_t ctor_show(struct kmem_cache *s, char *buf)
> {
> @@ -4644,6 +4678,7 @@ static ssize_t objects_partial_show(stru
> }
> SLAB_ATTR_RO(objects_partial);
>
> +#ifdef CONFIG_SLUB_CPU_PARTIAL
> static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
> {
> int objects = 0;
> @@ -4674,6 +4709,7 @@ static ssize_t slabs_cpu_partial_show(st
> return len + sprintf(buf + len, "\n");
> }
> SLAB_ATTR_RO(slabs_cpu_partial);
> +#endif
>
> static ssize_t reclaim_account_show(struct kmem_cache *s, char *buf)
> {
> @@ -4997,11 +5033,13 @@ STAT_ATTR(DEACTIVATE_BYPASS, deactivate_
> STAT_ATTR(ORDER_FALLBACK, order_fallback);
> STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);
> STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
> +#ifdef CONFIG_CPU_PARTIAL

...the same here, and ...

> STAT_ATTR(CPU_PARTIAL_ALLOC, cpu_partial_alloc);
> STAT_ATTR(CPU_PARTIAL_FREE, cpu_partial_free);
> STAT_ATTR(CPU_PARTIAL_NODE, cpu_partial_node);
> STAT_ATTR(CPU_PARTIAL_DRAIN, cpu_partial_drain);
> #endif
> +#endif
>
> static struct attribute *slab_attrs[] = {
> &slab_size_attr.attr,
> @@ -5009,7 +5047,9 @@ static struct attribute *slab_attrs[] =
> &objs_per_slab_attr.attr,
> &order_attr.attr,
> &min_partial_attr.attr,
> +#ifdef CONFIG_CPU_PARTIAL

...here too. All should be CONFIG_SLUB_CPU_PARTIAL

Thanks,
Paul.
--

> &cpu_partial_attr.attr,
> +#endif
> &objects_attr.attr,
> &objects_partial_attr.attr,
> &partial_attr.attr,
> @@ -5022,7 +5062,9 @@ static struct attribute *slab_attrs[] =
> &destroy_by_rcu_attr.attr,
> &shrink_attr.attr,
> &reserved_attr.attr,
> +#ifdef CONFIG_SLUB_CPU_PARTIAL
> &slabs_cpu_partial_attr.attr,
> +#endif
> #ifdef CONFIG_SLUB_DEBUG
> &total_objects_attr.attr,
> &slabs_attr.attr,
> @@ -5064,11 +5106,13 @@ static struct attribute *slab_attrs[] =
> &order_fallback_attr.attr,
> &cmpxchg_double_fail_attr.attr,
> &cmpxchg_double_cpu_fail_attr.attr,
> +#ifdef CONFIG_SLUB_CPU_PARTIAL
> &cpu_partial_alloc_attr.attr,
> &cpu_partial_free_attr.attr,
> &cpu_partial_node_attr.attr,
> &cpu_partial_drain_attr.attr,
> #endif
> +#endif
> #ifdef CONFIG_FAILSLAB
> &failslab_attr.attr,
> #endif
> Index: linux/init/Kconfig
> ===================================================================
> --- linux.orig/init/Kconfig 2013-04-01 10:27:05.908964674 -0500
> +++ linux/init/Kconfig 2013-04-01 10:31:46.497863625 -0500
> @@ -1514,6 +1514,17 @@ config SLOB
>
> endchoice
>
> +config SLUB_CPU_PARTIAL
> + default y
> + depends on SLUB
> + bool "SLUB per cpu partial cache"
> + help
> + Per cpu partial caches accellerate objects allocation and freeing
> + that is local to a processor at the price of more indeterminism
> + in the latency of the free. On overflow these caches will be cleared
> + which requires the taking of locks that may cause latency spikes.
> + Typically one would choose no for a realtime system.
> +
> config MMAP_ALLOW_UNINITIALIZED
> bool "Allow mmapped anonymous memory to be uninitialized"
> depends on EXPERT && !MMU
>


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