linux-kernel - Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty

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Date:	Wed, 25 Sep 2013 22:53:22 +0800
From:	Lin Ming <minggr@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>, lkp@...org,
	Tejun Heo <tj@...nel.org>
Subject: Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data"

On Wed, Sep 25, 2013 at 7:30 PM, Peter Hurley <peter@...leysoftware.com> wrote:
> On 09/25/2013 05:04 AM, Lin Ming wrote:
>>
>> On Wed, Sep 18, 2013 at 8:22 AM, Peter Hurley <peter@...leysoftware.com>
>> wrote:
>> [snip]
>>>
>>>
>>> Looking over vmalloc.c, the critical section footprint of the
>>> vmap_area_lock
>>> could definitely be reduced (even nearly eliminated), but that's a
>>> project
>>> for
>>> another day :)
>>
>>
>> Hi Peter,
>>
>> I also looked over vmallo.c, but didn't find obvious way to reduce the
>> critical section footprint.
>> Could you share some hints how to do this?
>
>
> vmap_area_list is an RCU list.
> get_vmalloc_info() doesn't need to take the vmap_area_lock at all.
> Look at __purge_vmap_area_lazy() for a howto.

Looking at it now ...

Thanks,
Lin Ming

>
> Regards,
> Peter Hurley
>
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