From: Michal Hocko <mhocko@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Ye Xiaolong <xiaolong.ye@intel.com>,
Vladimir Davydov <vdavydov@virtuozzo.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH rebase] mm: fix vm-scalability regression in cgroup-aware workingset code
Date: Mon, 27 Jun 2016 15:05:28 +0200 [thread overview]
Message-ID: <20160627130527.GK31799@dhcp22.suse.cz> (raw)
In-Reply-To: <20160624175101.GA3024@cmpxchg.org>
[Sorry for a late reply]
On Fri 24-06-16 13:51:01, Johannes Weiner wrote:
> This is a rebased version on top of mmots sans the nodelru stuff.
>
> ---
>
> 23047a96d7cf ("mm: workingset: per-cgroup cache thrash detection")
> added a page->mem_cgroup lookup to the cache eviction, refault, and
> activation paths, as well as locking to the activation path, and the
> vm-scalability tests showed a regression of -23%. While the test in
> question is an artificial worst-case scenario that doesn't occur in
> real workloads - reading two sparse files in parallel at full CPU
> speed just to hammer the LRU paths - there is still some optimizations
> that can be done in those paths.
>
> Inline the lookup functions to eliminate calls. Also, page->mem_cgroup
> doesn't need to be stabilized when counting an activation; we merely
> need to hold the RCU lock to prevent the memcg from being freed.
>
> This cuts down on overhead quite a bit:
>
> 23047a96d7cfcfca 063f6715e77a7be5770d6081fe
> ---------------- --------------------------
> %stddev %change %stddev
> \ | \
> 21621405 +- 0% +11.3% 24069657 +- 2% vm-scalability.throughput
>
> Reported-by: Ye Xiaolong <xiaolong.ye@intel.com>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Minor note below
> +static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
> +{
I guess rcu_read_lock_held() here would be appropriate
> + return READ_ONCE(page->mem_cgroup);
> +}
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-06-27 13:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-22 18:20 [PATCH] mm: fix vm-scalability regression in cgroup-aware workingset code Johannes Weiner
2016-06-24 17:51 ` [PATCH rebase] " Johannes Weiner
2016-06-27 13:05 ` Michal Hocko [this message]
2016-07-07 19:40 ` Johannes Weiner
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