1 files changed, 223 insertions, 0 deletions
diff --git a/debian/patches-rt/0199-mm-SLUB-delay-giving-back-empty-slubs-to-IRQ-enabled.patch b/debian/patches-rt/0199-mm-SLUB-delay-giving-back-empty-slubs-to-IRQ-enabled.patch
new file mode 100644
index 000000000..8af579dea
--- /dev/null
+++ b/debian/patches-rt/0199-mm-SLUB-delay-giving-back-empty-slubs-to-IRQ-enabled.patch
@@ -0,0 +1,223 @@
+From e620c8c3d37a6e6ff999f303521997d2950a71cd Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Thu, 21 Jun 2018 17:29:19 +0200
+Subject: [PATCH 199/323] mm/SLUB: delay giving back empty slubs to IRQ enabled
+ regions
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+__free_slab() is invoked with disabled interrupts which increases the
+irq-off time while __free_pages() is doing the work.
+Allow __free_slab() to be invoked with enabled interrupts and move
+everything from interrupts-off invocations to a temporary per-CPU list
+so it can be processed later.
+
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ mm/slub.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++----
+ 1 file changed, 69 insertions(+), 5 deletions(-)
+
+diff --git a/mm/slub.c b/mm/slub.c
+index 863554db3323..faba29039375 100644
+--- a/mm/slub.c
++++ b/mm/slub.c
+@@ -1494,6 +1494,12 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
+ }
+ #endif /* CONFIG_SLUB_DEBUG */
+ 
++struct slub_free_list {
++	raw_spinlock_t		lock;
++	struct list_head	list;
++};
++static DEFINE_PER_CPU(struct slub_free_list, slub_free_list);
++
+ /*
+  * Hooks for other subsystems that check memory allocations. In a typical
+  * production configuration these hooks all should produce no code at all.
+@@ -1849,6 +1855,16 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
+ 	__free_pages(page, order);
+ }
+ 
++static void free_delayed(struct list_head *h)
++{
++	while (!list_empty(h)) {
++		struct page *page = list_first_entry(h, struct page, lru);
++
++		list_del(&page->lru);
++		__free_slab(page->slab_cache, page);
++	}
++}
++
+ static void rcu_free_slab(struct rcu_head *h)
+ {
+ 	struct page *page = container_of(h, struct page, rcu_head);
+@@ -1860,6 +1876,12 @@ static void free_slab(struct kmem_cache *s, struct page *page)
+ {
+ 	if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) {
+ 		call_rcu(&page->rcu_head, rcu_free_slab);
++	} else if (irqs_disabled()) {
++		struct slub_free_list *f = this_cpu_ptr(&slub_free_list);
++
++		raw_spin_lock(&f->lock);
++		list_add(&page->lru, &f->list);
++		raw_spin_unlock(&f->lock);
+ 	} else
+ 		__free_slab(s, page);
+ }
+@@ -2392,14 +2414,21 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
+ 			pobjects = oldpage->pobjects;
+ 			pages = oldpage->pages;
+ 			if (drain && pobjects > slub_cpu_partial(s)) {
++				struct slub_free_list *f;
+ 				unsigned long flags;
++				LIST_HEAD(tofree);
+ 				/*
+ 				 * partial array is full. Move the existing
+ 				 * set to the per node partial list.
+ 				 */
+ 				local_irq_save(flags);
+ 				unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
++				f = this_cpu_ptr(&slub_free_list);
++				raw_spin_lock(&f->lock);
++				list_splice_init(&f->list, &tofree);
++				raw_spin_unlock(&f->lock);
+ 				local_irq_restore(flags);
++				free_delayed(&tofree);
+ 				oldpage = NULL;
+ 				pobjects = 0;
+ 				pages = 0;
+@@ -2465,7 +2494,22 @@ static bool has_cpu_slab(int cpu, void *info)
+ 
+ static void flush_all(struct kmem_cache *s)
+ {
++	LIST_HEAD(tofree);
++	int cpu;
++
+ 	on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1);
++	for_each_online_cpu(cpu) {
++		struct slub_free_list *f;
++
++		if (!has_cpu_slab(cpu, s))
++			continue;
++
++		f = &per_cpu(slub_free_list, cpu);
++		raw_spin_lock_irq(&f->lock);
++		list_splice_init(&f->list, &tofree);
++		raw_spin_unlock_irq(&f->lock);
++		free_delayed(&tofree);
++	}
+ }
+ 
+ /*
+@@ -2662,8 +2706,10 @@ static inline void *get_freelist(struct kmem_cache *s, struct page *page)
+  * already disabled (which is the case for bulk allocation).
+  */
+ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
+-			  unsigned long addr, struct kmem_cache_cpu *c)
++			  unsigned long addr, struct kmem_cache_cpu *c,
++			  struct list_head *to_free)
+ {
++	struct slub_free_list *f;
+ 	void *freelist;
+ 	struct page *page;
+ 
+@@ -2732,6 +2778,13 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
+ 	VM_BUG_ON(!c->page->frozen);
+ 	c->freelist = get_freepointer(s, freelist);
+ 	c->tid = next_tid(c->tid);
++
++out:
++	f = this_cpu_ptr(&slub_free_list);
++	raw_spin_lock(&f->lock);
++	list_splice_init(&f->list, to_free);
++	raw_spin_unlock(&f->lock);
++
+ 	return freelist;
+ 
+ new_slab:
+@@ -2747,7 +2800,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
+ 
+ 	if (unlikely(!freelist)) {
+ 		slab_out_of_memory(s, gfpflags, node);
+-		return NULL;
++		goto out;
+ 	}
+ 
+ 	page = c->page;
+@@ -2760,7 +2813,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
+ 		goto new_slab;	/* Slab failed checks. Next slab needed */
+ 
+ 	deactivate_slab(s, page, get_freepointer(s, freelist), c);
+-	return freelist;
++	goto out;
+ }
+ 
+ /*
+@@ -2772,6 +2825,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
+ {
+ 	void *p;
+ 	unsigned long flags;
++	LIST_HEAD(tofree);
+ 
+ 	local_irq_save(flags);
+ #ifdef CONFIG_PREEMPTION
+@@ -2783,8 +2837,9 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
+ 	c = this_cpu_ptr(s->cpu_slab);
+ #endif
+ 
+-	p = ___slab_alloc(s, gfpflags, node, addr, c);
++	p = ___slab_alloc(s, gfpflags, node, addr, c, &tofree);
+ 	local_irq_restore(flags);
++	free_delayed(&tofree);
+ 	return p;
+ }
+ 
+@@ -3282,6 +3337,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
+ 			  void **p)
+ {
+ 	struct kmem_cache_cpu *c;
++	LIST_HEAD(to_free);
+ 	int i;
+ 	struct obj_cgroup *objcg = NULL;
+ 
+@@ -3315,7 +3371,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
+ 			 * of re-populating per CPU c->freelist
+ 			 */
+ 			p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE,
+-					    _RET_IP_, c);
++					    _RET_IP_, c, &to_free);
+ 			if (unlikely(!p[i]))
+ 				goto error;
+ 
+@@ -3330,6 +3386,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
+ 	}
+ 	c->tid = next_tid(c->tid);
+ 	local_irq_enable();
++	free_delayed(&to_free);
+ 
+ 	/* Clear memory outside IRQ disabled fastpath loop */
+ 	if (unlikely(slab_want_init_on_alloc(flags, s))) {
+@@ -3344,6 +3401,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
+ 	return i;
+ error:
+ 	local_irq_enable();
++	free_delayed(&to_free);
+ 	slab_post_alloc_hook(s, objcg, flags, i, p);
+ 	__kmem_cache_free_bulk(s, i, p);
+ 	return 0;
+@@ -4361,6 +4419,12 @@ void __init kmem_cache_init(void)
+ {
+ 	static __initdata struct kmem_cache boot_kmem_cache,
+ 		boot_kmem_cache_node;
++	int cpu;
++
++	for_each_possible_cpu(cpu) {
++		raw_spin_lock_init(&per_cpu(slub_free_list, cpu).lock);
++		INIT_LIST_HEAD(&per_cpu(slub_free_list, cpu).list);
++	}
+ 
+ 	if (debug_guardpage_minorder())
+ 		slub_max_order = 0;
+-- 
+2.43.0
+