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Date: Wed, 17 Jan 2018 06:17:04 -0800
From: Matthew Wilcox <willy@infradead.org>
To: Xishi Qiu <qiuxishi@huawei.com>
Cc: Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@kernel.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        "Wujiangtao (A)" <wu.wujiangtao@huawei.com>
Subject: Re: [RFC] mm: why vfree() do not free page table memory?
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On Wed, Jan 17, 2018 at 05:48:57PM +0800, Xishi Qiu wrote:
> > Did you notice an actual issue, or is this just theoretical concern.
> 
> Yes, we have this problem on our production line.
> I find the page table memory takes 200-300M.

200MB?  That's mapping 800GB of virtual address space.  That must be
quite the module you're loading there ...