From: Xunlei Pang <xlpang@linux.alibaba.com>
To: Christoph Lameter <cl@gentwo.de>, Xunlei Pang <xlpang@linux.alibaba.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Wen Yang <wenyang@linux.alibaba.com>,
Roman Gushchin <guro@fb.com>, Pekka Enberg <penberg@gmail.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH v2 3/3] mm/slub: Use percpu partial free counter
Date: Wed, 3 Mar 2021 21:46:36 +0800 [thread overview]
Message-ID: <1c61e8fb-98ef-6d5f-12d7-ab5f16890e17@linux.alibaba.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2103021012010.860725@gentwo.de>
On 3/2/21 5:14 PM, Christoph Lameter wrote:
> On Mon, 10 Aug 2020, Xunlei Pang wrote:
>
>>
>> diff --git a/mm/slab.h b/mm/slab.h
>> index c85e2fa..a709a70 100644
>> --- a/mm/slab.h
>> +++ b/mm/slab.h
>> @@ -616,7 +616,7 @@ struct kmem_cache_node {
>> #ifdef CONFIG_SLUB
>> unsigned long nr_partial;
>> struct list_head partial;
>> - atomic_long_t partial_free_objs;
>> + atomic_long_t __percpu *partial_free_objs;
>
> A percpu counter is never atomic. Just use unsigned long and use this_cpu
> operations for this thing. That should cut down further on the overhead.
>
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1775,11 +1775,21 @@ static void discard_slab(struct kmem_cache *s, struct page *page)
>> /*
>> * Management of partially allocated slabs.
>> */
>> +static inline long get_partial_free(struct kmem_cache_node *n)
>> +{
>> + long nr = 0;
>> + int cpu;
>> +
>> + for_each_possible_cpu(cpu)
>> + nr += atomic_long_read(per_cpu_ptr(n->partial_free_objs, cpu));
>
> this_cpu_read(*n->partial_free_objs)
>
>> static inline void
>> __update_partial_free(struct kmem_cache_node *n, long delta)
>> {
>> - atomic_long_add(delta, &n->partial_free_objs);
>> + atomic_long_add(delta, this_cpu_ptr(n->partial_free_objs));
>
> this_cpu_add()
>
> and so on.
>
Thanks, I changed them both to use "unsigned long", and will send v3 out
after our internal performance regression test passes.
next prev parent reply other threads:[~2021-03-03 18:11 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-10 12:17 [PATCH v2 0/3] mm/slub: Fix count_partial() problem Xunlei Pang
2020-08-10 12:17 ` [PATCH v2 1/3] mm/slub: Introduce two counters for partial objects Xunlei Pang
2020-08-10 12:17 ` [PATCH v2 2/3] mm/slub: Get rid of count_partial() Xunlei Pang
2020-08-10 12:17 ` [PATCH v2 3/3] mm/slub: Use percpu partial free counter Xunlei Pang
2021-03-02 5:56 ` Shu Ming
2021-03-02 9:14 ` Christoph Lameter
2021-03-03 13:46 ` Xunlei Pang [this message]
2021-03-03 14:26 ` Matthew Wilcox
2021-03-03 19:15 ` Christoph Lameter
2021-03-03 19:30 ` Matthew Wilcox
2021-03-03 19:55 ` Christoph Lameter
2021-03-03 20:16 ` Matthew Wilcox
2020-08-20 14:02 ` [PATCH v2 0/3] mm/slub: Fix count_partial() problem Pekka Enberg
2020-08-24 10:04 ` xunlei
2021-03-01 10:31 ` Shu Ming
2021-03-03 13:34 ` Xunlei Pang
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