From: Andrew Morton <akpm@linux-foundation.org>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Zhang Yanfei <zhangyanfei.yes@gmail.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Andi Kleen <andi@firstfloor.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Richard Yao <ryao@gentoo.org>
Subject: Re: [PATCH] vmalloc: use rcu list iterator to reduce vmap_area_lock contention
Date: Thu, 29 May 2014 13:05:44 -0700 [thread overview]
Message-ID: <20140529130544.56213f048f331723329ff828@linux-foundation.org> (raw)
In-Reply-To: <1401344554-3596-1-git-send-email-iamjoonsoo.kim@lge.com>
On Thu, 29 May 2014 15:22:34 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
> Richard Yao reported a month ago that his system have a trouble
> with vmap_area_lock contention during performance analysis
> by /proc/meminfo. Andrew asked why his analysis checks /proc/meminfo
> stressfully, but he didn't answer it.
>
> https://lkml.org/lkml/2014/4/10/416
>
> Although I'm not sure that this is right usage or not, there is a solution
> reducing vmap_area_lock contention with no side-effect. That is just
> to use rcu list iterator in get_vmalloc_info(). This function only needs
> values on vmap_area structure, so we don't need to grab a spinlock.
The mixture of rcu protection and spinlock protection for
vmap_area_list is pretty confusing. Are you able to describe the
overall design here? When and why do we use one versus the other?
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next prev parent reply other threads:[~2014-05-29 20:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-29 6:22 Joonsoo Kim
2014-05-29 12:56 ` Eric Dumazet
2014-05-29 13:17 ` Richard Yao
2014-05-29 20:05 ` Andrew Morton [this message]
2014-05-29 21:23 ` Eric Dumazet
2014-05-30 0:43 ` Joonsoo Kim
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