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From: Hillf Danton <hdanton@sina.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [RFC v2 29/34] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context
Date: Wed,  7 Jul 2021 14:33:04 +0800	[thread overview]
Message-ID: <20210707063304.2074-1-hdanton@sina.com> (raw)
In-Reply-To: <20210609113903.1421-30-vbabka@suse.cz>

On Wed,  9 Jun 2021 13:38:58 +0200
>From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
>flush_all() flushes a specific SLAB cache on each CPU (where the cache
>is present). The deactivate_slab()/__free_slab() invocation happens
>within IPI handler and is problematic for PREEMPT_RT.
>
>The flush operation is not a frequent operation or a hot path. The
>per-CPU flush operation can be moved to within a workqueue.
>
>[vbabka@suse.cz: adapt to new SLUB changes]
>Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
>---
> mm/slub.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 48 insertions(+), 8 deletions(-)
>
>diff --git a/mm/slub.c b/mm/slub.c
>index 5c70fc17e9be..6e747e0d7dcd 100644
>--- a/mm/slub.c
>+++ b/mm/slub.c
>@@ -2474,33 +2474,73 @@ static inline void __flush_cpu_slab(struct kmem_c=
>ache *s, int cpu)
> 	unfreeze_partials_cpu(s, c);
> }
>
>+struct slub_flush_work {
>+	struct work_struct work;
>+	struct kmem_cache *s;
>+	bool skip;
>+};
>+
> /*
>  * Flush cpu slab.
>  *
>- * Called from IPI handler with interrupts disabled.
>+ * Called from CPU work handler with migration disabled.
>  */

The comment muddies a pint more than it could clear up - kworkers do their
works without an eye on cpuhp. It is fine just to cut it given the
cpus_read_lock() in flush_all().

>-static void flush_cpu_slab(void *d)
>+static void flush_cpu_slab(struct work_struct *w)
> {
>-	struct kmem_cache *s = d;
>-	struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
>+	struct kmem_cache *s;
>+	struct kmem_cache_cpu *c;
>+	struct slub_flush_work *sfw;
>+
>+	sfw = container_of(w, struct slub_flush_work, work);
>+
>+	s = sfw->s;
>+	c = this_cpu_ptr(s->cpu_slab);
>
> 	if (c->page)
>-		flush_slab(s, c, false);
>+		flush_slab(s, c, true);
>
> 	unfreeze_partials(s);
> }
>
>-static bool has_cpu_slab(int cpu, void *info)
>+static bool has_cpu_slab(int cpu, struct kmem_cache *s)
> {
>-	struct kmem_cache *s = info;
> 	struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
>
> 	return c->page || slub_percpu_partial(c);
> }
>
>+static DEFINE_MUTEX(flush_lock);
>+static DEFINE_PER_CPU(struct slub_flush_work, slub_flush);
>+
> static void flush_all(struct kmem_cache *s)
> {
>-	on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1);
>+	struct slub_flush_work *sfw;
>+	unsigned int cpu;
>+
>+	cpus_read_lock();
>+	mutex_lock(&flush_lock);
>+
>+	for_each_online_cpu(cpu) {
>+		sfw = &per_cpu(slub_flush, cpu);
>+		if (!has_cpu_slab(cpu, s)) {
>+			sfw->skip = true;
>+			continue;
>+		}
>+		INIT_WORK(&sfw->work, flush_cpu_slab);
>+		sfw->skip = false;
>+		sfw->s = s;
>+		schedule_work_on(cpu, &sfw->work);
>+	}
>+
>+	for_each_online_cpu(cpu) {
>+		sfw = &per_cpu(slub_flush, cpu);
>+		if (sfw->skip)
>+			continue;
>+		flush_work(&sfw->work);
>+	}
>+
>+	mutex_unlock(&flush_lock);
>+	cpus_read_unlock();
> }
>
> /*
>--
>2.31.1


  parent reply	other threads:[~2021-07-07  6:33 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 ` [RFC v2 25/34] mm, slub: detach percpu partial list in unfreeze_partials() using this_cpu_cmpxchg() Vlastimil Babka
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 [this message]
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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