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slab: don't batch kvfree_rcu() with SLUB_TINY

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kvfree_rcu() is batched for better performance except on TINY_RCU, which
is a simple implementation for small UP systems. Similarly SLUB_TINY is
an option intended for small systems, whether or not used together with
TINY_RCU. In case SLUB_TINY is used with !TINY_RCU, it makes arguably
sense to not do the batching and limit the memory footprint. It's also
suboptimal to have RCU-specific #ifdefs in slab code.

With that, add CONFIG_KVFREE_RCU_BATCHED to determine whether batching
kvfree_rcu() implementation is used. It is not set by a user prompt, but
enabled by default and disabled in case TINY_RCU or SLUB_TINY are
enabled.

Use the new config for #ifdef's in slab code and extend their scope to
cover all code used by the batched kvfree_rcu(). For example there's no
need to perform kvfree_rcu_init() if the batching is disabled.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Vlastimil Babka
2025-02-03 10:28:50 +01:00
parent 49d5377b38
commit c9f8f1242a
3 changed files with 14 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
mm/slab_common.c
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@@ -1284,7 +1284,7 @@ EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
EXPORT_TRACEPOINT_SYMBOL(kfree);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
#ifdef CONFIG_TINY_RCU
#ifndef CONFIG_KVFREE_RCU_BATCHED
void kvfree_call_rcu(struct rcu_head *head, void *ptr)
{
@@ -1301,7 +1301,11 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr)
}
EXPORT_SYMBOL_GPL(kvfree_call_rcu);
#endif
void __init kvfree_rcu_init(void)
{
}
#else /* CONFIG_KVFREE_RCU_BATCHED */
/*
* This rcu parameter is runtime-read-only. It reflects
@@ -1879,8 +1883,6 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
return true;
}
#if !defined(CONFIG_TINY_RCU)
static enum hrtimer_restart
schedule_page_work_fn(struct hrtimer *t)
{
@@ -2089,8 +2091,6 @@ void kvfree_rcu_barrier(void)
}
EXPORT_SYMBOL_GPL(kvfree_rcu_barrier);
#endif /* #if !defined(CONFIG_TINY_RCU) */
static unsigned long
kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
@@ -2180,3 +2180,6 @@ void __init kvfree_rcu_init(void)
shrinker_register(kfree_rcu_shrinker);
}
#endif /* CONFIG_KVFREE_RCU_BATCHED */