linux-kernel - [RFC v2 22/34] mm, slub: move irq control into unfreeze

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Message-Id: <20210609113903.1421-23-vbabka@suse.cz>
Date:   Wed,  9 Jun 2021 13:38:51 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jann Horn <jannh@...gle.com>, Vlastimil Babka <vbabka@...e.cz>
Subject: [RFC v2 22/34] mm, slub: move irq control into unfreeze_partials()

unfreeze_partials() can be optimized so that it doesn't need irqs disabled for
the whole time. As the first step, move irq control into the function and
remove it from the put_cpu_partial() caller.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index a99a254f2410..4a3cd8174cd2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2290,9 +2290,8 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 /*
  * Unfreeze all the cpu partial slabs.
  *
- * This function must be called with interrupts disabled
- * for the cpu using c (or some other guarantee must be there
- * to guarantee no concurrent accesses).
+ * 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)
@@ -2300,6 +2299,9 @@ static void unfreeze_partials(struct kmem_cache *s,
 #ifdef CONFIG_SLUB_CPU_PARTIAL
 	struct kmem_cache_node *n = NULL, *n2 = NULL;
 	struct page *page, *discard_page = NULL;
+	unsigned long flags;
+
+	local_irq_save(flags);
 
 	while ((page = slub_percpu_partial(c))) {
 		struct page new;
@@ -2352,6 +2354,8 @@ static void unfreeze_partials(struct kmem_cache *s,
 		discard_slab(s, page);
 		stat(s, FREE_SLAB);
 	}
+
+	local_irq_restore(flags);
 #endif	/* CONFIG_SLUB_CPU_PARTIAL */
 }
 
@@ -2379,14 +2383,11 @@ 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)) {
-				unsigned long flags;
 				/*
 				 * 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));
-				local_irq_restore(flags);
 				oldpage = NULL;
 				pobjects = 0;
 				pages = 0;
-- 
2.31.1