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From: Vlastimil Babka <vbabka@suse.cz>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Christoph Lameter <cl@linux.com>,
	David Rientjes <rientjes@google.com>,
	Pekka Enberg <penberg@kernel.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mel Gorman <mgorman@techsingularity.net>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jann Horn <jannh@google.com>, Vlastimil Babka <vbabka@suse.cz>
Subject: [RFC v2 25/34] mm, slub: detach percpu partial list in unfreeze_partials() using this_cpu_cmpxchg()
Date: Wed,  9 Jun 2021 13:38:54 +0200	[thread overview]
Message-ID: <20210609113903.1421-26-vbabka@suse.cz> (raw)
In-Reply-To: <20210609113903.1421-1-vbabka@suse.cz>

Instead of relying on disabled irqs for atomicity when detaching the percpu
partial list, we can use this_cpu_cmpxchg() and detach without irqs disabled.
However, unfreeze_partials() can be also called from another cpu on behalf of
a cpu that is being offlined, so we need to restructure the code accordingly:

- __unfreeze_partials() is the bulk of unfreeze_partials() that processes the
  detached percpu partial list
- unfreeze_partials() uses this_cpu_cmpxchg() to detach list from current cpu
- unfreeze_partials_cpu() is to be called for the offlined cpu so it needs no
  protection, and is called from __flush_cpu_slab()
- flush_cpu_slab() is for the local cpu thus it needs to call
  unfreeze_partials(). So it can't simply call
  __flush_cpu_slab(smp_processor_id()) anymore and we have to open-code it

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 77 +++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 55 insertions(+), 22 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 3e0ec7211d55..0867801e3086 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2287,25 +2287,15 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 	}
 }
 
-/*
- * Unfreeze all the cpu partial slabs.
- *
- * This function must be called with preemption or migration
- * disabled with c local to the cpu.
- */
-static void unfreeze_partials(struct kmem_cache *s,
-		struct kmem_cache_cpu *c)
-{
 #ifdef CONFIG_SLUB_CPU_PARTIAL
+static void __unfreeze_partials(struct kmem_cache *s, struct page *partial_page)
+{
 	struct kmem_cache_node *n = NULL, *n2 = NULL;
-	struct page *page, *partial_page, *discard_page = NULL;
+	struct page *page, *discard_page = NULL;
 	unsigned long flags;
 
 	local_irq_save(flags);
 
-	partial_page = slub_percpu_partial(c);
-	c->partial = NULL;
-
 	while (partial_page) {
 		struct page new;
 		struct page old;
@@ -2360,10 +2350,49 @@ static void unfreeze_partials(struct kmem_cache *s,
 		discard_slab(s, page);
 		stat(s, FREE_SLAB);
 	}
+}
 
-#endif	/* CONFIG_SLUB_CPU_PARTIAL */
+/*
+ * Unfreeze all the cpu partial slabs.
+ *
+ * This function must be called with preemption or migration
+ * disabled.
+ */
+static void unfreeze_partials(struct kmem_cache *s)
+{
+	struct page *partial_page;
+
+	do {
+		partial_page = this_cpu_read(s->cpu_slab->partial);
+
+	} while (partial_page &&
+		 this_cpu_cmpxchg(s->cpu_slab->partial, partial_page, NULL)
+				  != partial_page);
+
+	if (partial_page)
+		__unfreeze_partials(s, partial_page);
 }
 
+static void unfreeze_partials_cpu(struct kmem_cache *s,
+				  struct kmem_cache_cpu *c)
+{
+	struct page *partial_page;
+
+	partial_page = slub_percpu_partial(c);
+	c->partial = NULL;
+
+	if (partial_page)
+		__unfreeze_partials(s, partial_page);
+}
+
+#else	/* CONFIG_SLUB_CPU_PARTIAL */
+
+static void unfreeze_partials(struct kmem_cache *s) { }
+static void unfreeze_partials_cpu(struct kmem_cache *s,
+				  struct kmem_cache_cpu *c) { }
+
+#endif	/* CONFIG_SLUB_CPU_PARTIAL */
+
 /*
  * Put a page that was just frozen (in __slab_free|get_partial_node) into a
  * partial page slot if available.
@@ -2392,7 +2421,7 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
 				 * partial array is full. Move the existing
 				 * set to the per node partial list.
 				 */
-				unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
+				unfreeze_partials(s);
 				oldpage = NULL;
 				pobjects = 0;
 				pages = 0;
@@ -2427,11 +2456,6 @@ static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
 	stat(s, CPUSLAB_FLUSH);
 }
 
-/*
- * Flush cpu slab.
- *
- * Called from IPI handler with interrupts disabled.
- */
 static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
 {
 	struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
@@ -2439,14 +2463,23 @@ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
 	if (c->page)
 		flush_slab(s, c);
 
-	unfreeze_partials(s, c);
+	unfreeze_partials_cpu(s, c);
 }
 
+/*
+ * Flush cpu slab.
+ *
+ * Called from IPI handler with interrupts disabled.
+ */
 static void flush_cpu_slab(void *d)
 {
 	struct kmem_cache *s = d;
+	struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
 
-	__flush_cpu_slab(s, smp_processor_id());
+	if (c->page)
+		flush_slab(s, c);
+
+	unfreeze_partials(s);
 }
 
 static bool has_cpu_slab(int cpu, void *info)
-- 
2.31.1


  parent reply	other threads:[~2021-06-09 11:41 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-09 11:38 [RFC v2 00/34] SLUB: reduce irq disabled scope and make it RT compatible Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 01/34] mm, slub: don't call flush_all() from list_locations() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 02/34] mm, slub: allocate private object map for sysfs listings Vlastimil Babka
2021-06-09 13:29   ` Christoph Lameter
2021-06-09 13:29     ` Christoph Lameter
2021-06-09 11:38 ` [RFC v2 03/34] mm, slub: allocate private object map for validate_slab_cache() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 04/34] mm, slub: don't disable irq for debug_check_no_locks_freed() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 05/34] mm, slub: remove redundant unfreeze_partials() from put_cpu_partial() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 06/34] mm, slub: unify cmpxchg_double_slab() and __cmpxchg_double_slab() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 07/34] mm, slub: extract get_partial() from new_slab_objects() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 08/34] mm, slub: dissolve new_slab_objects() into ___slab_alloc() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 09/34] mm, slub: return slab page from get_partial() and set c->page afterwards Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 10/34] mm, slub: restructure new page checks in ___slab_alloc() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 11/34] mm, slub: simplify kmem_cache_cpu and tid setup Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 12/34] mm, slub: move disabling/enabling irqs to ___slab_alloc() Vlastimil Babka
2021-07-06  4:38   ` Mike Galbraith
2021-07-06  4:38     ` Mike Galbraith
2021-06-09 11:38 ` [RFC v2 13/34] mm, slub: do initial checks in ___slab_alloc() with irqs enabled Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 14/34] mm, slub: move disabling irqs closer to get_partial() in ___slab_alloc() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 15/34] mm, slub: restore irqs around calling new_slab() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 16/34] mm, slub: validate slab from partial list or page allocator before making it cpu slab Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 17/34] mm, slub: check new pages with restored irqs Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 18/34] mm, slub: stop disabling irqs around get_partial() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 19/34] mm, slub: move reset of c->page and freelist out of deactivate_slab() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 20/34] mm, slub: make locking in deactivate_slab() irq-safe Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 21/34] mm, slub: call deactivate_slab() without disabling irqs Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 22/34] mm, slub: move irq control into unfreeze_partials() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 23/34] mm, slub: discard slabs in unfreeze_partials() without irqs disabled Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 24/34] mm, slub: detach whole partial list at once in unfreeze_partials() Vlastimil Babka
2021-06-09 11:38 ` Vlastimil Babka [this message]
2021-06-09 11:38 ` [RFC v2 26/34] mm, slub: only disable irq with spin_lock in __unfreeze_partials() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 27/34] mm, slub: don't disable irqs in slub_cpu_dead() Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 28/34] mm, slab: make flush_slab() possible to call with irqs enabled Vlastimil Babka
2021-06-09 11:38 ` [RFC v2 29/34] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context Vlastimil Babka
2021-06-09 22:29   ` Cyrill Gorcunov
2021-06-10  8:32     ` Vlastimil Babka
2021-06-10  8:36       ` Cyrill Gorcunov
2021-07-07  6:33   ` Hillf Danton
2021-06-09 11:38 ` [RFC v2 30/34] mm: slub: Make object_map_lock a raw_spinlock_t Vlastimil Babka
2021-06-09 11:39 ` [RFC v2 31/34] mm, slub: optionally save/restore irqs in slab_[un]lock()/ Vlastimil Babka
2021-07-02 12:17   ` Sebastian Andrzej Siewior
2021-06-09 11:39 ` [RFC v2 32/34] mm, slub: make slab_lock() disable irqs with PREEMPT_RT Vlastimil Babka
2021-06-09 11:39 ` [RFC v2 33/34] mm, slub: use migrate_disable() on PREEMPT_RT Vlastimil Babka
2021-06-14 11:07   ` Vlastimil Babka
2021-06-14 11:16     ` Sebastian Andrzej Siewior
2021-06-14 11:33       ` Vlastimil Babka
2021-06-14 12:54         ` Vlastimil Babka
2021-06-14 14:01         ` Sebastian Andrzej Siewior
2021-06-09 11:39 ` [RFC v2 34/34] mm, slub: convert kmem_cpu_slab protection to local_lock Vlastimil Babka
2021-06-14  9:49 ` [RFC v2 00/34] SLUB: reduce irq disabled scope and make it RT compatible Mel Gorman
2021-06-14 11:31   ` Mel Gorman
2021-06-14 11:10 ` Vlastimil Babka
2021-07-02 18:29 ` Sebastian Andrzej Siewior
2021-07-02 20:25   ` Vlastimil Babka
2021-07-29 13:49     ` Sebastian Andrzej Siewior
2021-07-29 14:17       ` Vlastimil Babka
2021-07-29 14:37         ` Sebastian Andrzej Siewior
2021-07-03  7:24   ` Mike Galbraith
2021-07-03 15:47     ` Mike Galbraith
2021-07-04  5:37       ` Mike Galbraith
2021-07-18  7:41     ` Vlastimil Babka
2021-07-18  8:29       ` Mike Galbraith
2021-07-18 12:09         ` Mike Galbraith
2021-07-05 16:00   ` Mike Galbraith
2021-07-06 17:56     ` Mike Galbraith

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