From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Richard Yao <ryao@gentoo.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Zhang Yanfei <zhangyanfei.yes@gmail.com>,
Wanpeng Li <liwanp@linux.vnet.ibm.com>,
Johannes Weiner <hannes@cmpxchg.org>,
HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel@gentoo.org, Matthew Thode <mthode@mthode.org>
Subject: Re: [PATCH] mm/vmalloc: Introduce DEBUG_VMALLOCINFO to reduce spinlock contention
Date: Wed, 16 Apr 2014 09:28:04 +0900 [thread overview]
Message-ID: <20140416002804.GB17350@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <1397148058-8737-1-git-send-email-ryao@gentoo.org>
On Thu, Apr 10, 2014 at 12:40:58PM -0400, Richard Yao wrote:
> Performance analysis of software compilation by Gentoo portage on an
> Intel E5-2620 with 64GB of RAM revealed that a sizeable amount of time,
> anywhere from 5% to 15%, was spent in get_vmalloc_info(), with at least
> 40% of that time spent in the _raw_spin_lock() invoked by it.
>
> The spinlock call is done on vmap_area_lock to protect vmap_area_list,
> but changes to vmap_area_list are made under RCU. The only consumer that
> requires a spinlock on an RCU-ified list is /proc/vmallocinfo. That is
Why only '/proc/vmallocinfo' needs the spinlock?
List iterators which access va->vm such as vread() and vwrite() needs
the spinlock too.
But, I think that get_vmalloc_info() doesn't need it, so you can use
rcu list iteration on that function and it would fix your problem.
Thanks.
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next prev parent reply other threads:[~2014-04-16 0:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-10 16:40 Richard Yao
2014-04-10 16:51 ` Andi Kleen
2014-04-10 17:09 ` Richard Yao
2014-04-16 0:28 ` Joonsoo Kim [this message]
2014-04-17 23:18 ` Andrew Morton
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