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From: Vlastimil Babka <vbabka@suse.cz>
To: linux-mm@kvack.org, Christoph Lameter <cl@linux.com>,
	David Rientjes <rientjes@google.com>,
	Pekka Enberg <penberg@kernel.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, Mike Galbraith <efault@gmx.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mel Gorman <mgorman@techsingularity.net>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: [PATCH v6 24/33] mm, slub: separate detaching of partial list in unfreeze_partials() from unfreezing
Date: Sat,  4 Sep 2021 12:49:54 +0200	[thread overview]
Message-ID: <20210904105003.11688-25-vbabka@suse.cz> (raw)
In-Reply-To: <20210904105003.11688-1-vbabka@suse.cz>

Unfreezing partial list can be split to two phases - detaching the list from
struct kmem_cache_cpu, and processing the list. The whole operation does not
need to be protected by disabled irqs. Restructure the code to separate the
detaching (with disabled irqs) and unfreezing (with irq disabling to be reduced
in the next patch).

Also, unfreeze_partials() can be called from another cpu on behalf of a cpu
that is being offlined, where disabling irqs on the local cpu has no sense, so
restructure the code as follows:

- __unfreeze_partials() is the bulk of unfreeze_partials() that processes the
  detached percpu partial list
- unfreeze_partials() detaches list from current cpu with irqs disabled and
  calls __unfreeze_partials()
- unfreeze_partials_cpu() is to be called for the offlined cpu so it needs no
  irq disabling, 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 the
  proper calls.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 73 ++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 51 insertions(+), 22 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index b31e00eb9561..9b46d9b9c879 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2347,25 +2347,15 @@ 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;
@@ -2420,10 +2410,45 @@ 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.
+ */
+static void unfreeze_partials(struct kmem_cache *s)
+{
+	struct page *partial_page;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	partial_page = this_cpu_read(s->cpu_slab->partial);
+	this_cpu_write(s->cpu_slab->partial, NULL);
+	local_irq_restore(flags);
+
+	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 inline void unfreeze_partials(struct kmem_cache *s) { }
+static inline 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.
@@ -2452,7 +2477,7 @@ 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;
@@ -2487,11 +2512,6 @@ 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);
@@ -2499,14 +2519,23 @@ 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)
-- 
2.33.0


  parent reply	other threads:[~2021-09-04 10:51 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-04 10:49 [PATCH v6 00/33] SLUB: reduce irq disabled scope and make it RT compatible Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 01/33] mm, slub: don't call flush_all() from slab_debug_trace_open() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 02/33] mm, slub: allocate private object map for debugfs listings Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 03/33] mm, slub: allocate private object map for validate_slab_cache() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 04/33] mm, slub: don't disable irq for debug_check_no_locks_freed() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 05/33] mm, slub: remove redundant unfreeze_partials() from put_cpu_partial() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 06/33] mm, slub: extract get_partial() from new_slab_objects() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 07/33] mm, slub: dissolve new_slab_objects() into ___slab_alloc() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 08/33] mm, slub: return slab page from get_partial() and set c->page afterwards Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 09/33] mm, slub: restructure new page checks in ___slab_alloc() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 10/33] mm, slub: simplify kmem_cache_cpu and tid setup Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 11/33] mm, slub: move disabling/enabling irqs to ___slab_alloc() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 12/33] mm, slub: do initial checks in ___slab_alloc() with irqs enabled Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 13/33] mm, slub: move disabling irqs closer to get_partial() in ___slab_alloc() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 14/33] mm, slub: restore irqs around calling new_slab() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 15/33] mm, slub: validate slab from partial list or page allocator before making it cpu slab Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 16/33] mm, slub: check new pages with restored irqs Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 17/33] mm, slub: stop disabling irqs around get_partial() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 18/33] mm, slub: move reset of c->page and freelist out of deactivate_slab() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 19/33] mm, slub: make locking in deactivate_slab() irq-safe Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 20/33] mm, slub: call deactivate_slab() without disabling irqs Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 21/33] mm, slub: move irq control into unfreeze_partials() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 22/33] mm, slub: discard slabs in unfreeze_partials() without irqs disabled Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 23/33] mm, slub: detach whole partial list at once in unfreeze_partials() Vlastimil Babka
2021-09-04 10:49 ` Vlastimil Babka [this message]
2021-09-04 10:49 ` [PATCH v6 25/33] mm, slub: only disable irq with spin_lock in __unfreeze_partials() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 26/33] mm, slub: don't disable irqs in slub_cpu_dead() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 27/33] mm, slab: split out the cpu offline variant of flush_slab() Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 28/33] mm: slub: move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context Vlastimil Babka
2021-09-04 10:49 ` [PATCH v6 29/33] mm: slub: make object_map_lock a raw_spinlock_t Vlastimil Babka
2021-09-04 10:50 ` [PATCH v6 30/33] mm, slub: make slab_lock() disable irqs with PREEMPT_RT Vlastimil Babka
2021-09-04 10:50 ` [PATCH v6 31/33] mm, slub: protect put_cpu_partial() with disabled irqs instead of cmpxchg Vlastimil Babka
2021-09-04 10:50 ` [PATCH v6 32/33] mm, slub: use migrate_disable() on PREEMPT_RT Vlastimil Babka
2021-09-04 10:50 ` [PATCH v6 33/33] mm, slub: convert kmem_cpu_slab protection to local_lock Vlastimil Babka
2021-09-05 14:16 ` [PATCH v6 00/33] SLUB: reduce irq disabled scope and make it RT compatible Mike Galbraith
2021-09-07  8:20 ` Mel Gorman

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