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From: Shakeel Butt <shakeelb@google.com>
To: Waiman Long <longman@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Cgroups <cgroups@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
	Muchun Song <songmuchun@bytedance.com>,
	Alex Shi <alex.shi@linux.alibaba.com>,
	Chris Down <chris@chrisdown.name>,
	Yafang Shao <laoar.shao@gmail.com>,
	Wei Yang <richard.weiyang@gmail.com>,
	Masayoshi Mizuma <msys.mizuma@gmail.com>,
	Xing Zhengjun <zhengjun.xing@linux.intel.com>,
	Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH-next v5 3/4] mm/memcg: Improve refill_obj_stock() performance
Date: Mon, 26 Apr 2021 12:24:02 -0700	[thread overview]
Message-ID: <CALvZod7_NtptXi=1QdfgyobL-bw72xGeZ9Sm3pn1pxtZ9crTow@mail.gmail.com> (raw)
In-Reply-To: <20210420192907.30880-4-longman@redhat.com>

On Tue, Apr 20, 2021 at 12:30 PM Waiman Long <longman@redhat.com> wrote:
>
> There are two issues with the current refill_obj_stock() code. First of
> all, when nr_bytes reaches over PAGE_SIZE, it calls drain_obj_stock() to
> atomically flush out remaining bytes to obj_cgroup, clear cached_objcg
> and do a obj_cgroup_put(). It is likely that the same obj_cgroup will
> be used again which leads to another call to drain_obj_stock() and
> obj_cgroup_get() as well as atomically retrieve the available byte from
> obj_cgroup. That is costly. Instead, we should just uncharge the excess
> pages, reduce the stock bytes and be done with it. The drain_obj_stock()
> function should only be called when obj_cgroup changes.
>
> Secondly, when charging an object of size not less than a page in
> obj_cgroup_charge(), it is possible that the remaining bytes to be
> refilled to the stock will overflow a page and cause refill_obj_stock()
> to uncharge 1 page. To avoid the additional uncharge in this case,
> a new overfill flag is added to refill_obj_stock() which will be set
> when called from obj_cgroup_charge().
>
> A multithreaded kmalloc+kfree microbenchmark on a 2-socket 48-core
> 96-thread x86-64 system with 96 testing threads were run.  Before this
> patch, the total number of kilo kmalloc+kfree operations done for a 4k
> large object by all the testing threads per second were 4,304 kops/s
> (cgroup v1) and 8,478 kops/s (cgroup v2). After applying this patch, the
> number were 4,731 (cgroup v1) and 418,142 (cgroup v2) respectively. This
> represents a performance improvement of 1.10X (cgroup v1) and 49.3X
> (cgroup v2).
>
> Signed-off-by: Waiman Long <longman@redhat.com>

After incorporating Roman's suggestion, you can add:

Reviewed-by: Shakeel Butt <shakeelb@google.com>

  parent reply	other threads:[~2021-04-26 19:24 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-20 19:29 [PATCH-next v5 0/4] mm/memcg: Reduce kmemcache memory accounting overhead Waiman Long
2021-04-20 19:29 ` [PATCH-next v5 1/4] mm/memcg: Move mod_objcg_state() to memcontrol.c Waiman Long
2021-04-21 15:26   ` Shakeel Butt
2021-04-21 23:08   ` Roman Gushchin
2021-04-20 19:29 ` [PATCH-next v5 2/4] mm/memcg: Cache vmstat data in percpu memcg_stock_pcp Waiman Long
2021-04-21 23:28   ` Roman Gushchin
2021-04-22 16:58     ` Waiman Long
2021-04-23  1:56       ` Roman Gushchin
2021-04-23 16:52         ` Waiman Long
2021-04-20 19:29 ` [PATCH-next v5 3/4] mm/memcg: Improve refill_obj_stock() performance Waiman Long
2021-04-21 23:55   ` Roman Gushchin
2021-04-22 17:26     ` Waiman Long
2021-04-23  2:28       ` Roman Gushchin
2021-04-23 20:06         ` Waiman Long
2021-04-26 19:24   ` Shakeel Butt [this message]
2021-04-20 19:29 ` [PATCH-next v5 4/4] mm/memcg: Optimize user context object stock access Waiman Long

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