linux-kernel - Re: remap_file

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Message-Id: <20140519155336.86E93E009B@blue.fi.intel.com>
Date:	Mon, 19 May 2014 18:53:36 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Armin Rigo <arigo@...es.org>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Christoph Hellwig <hch@...radead.org>,
	Kenny Simpson <theonetruekenny@...il.com>,
	Michal Hocko <mhocko@...e.cz>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: remap_file_pages() use

Armin Rigo wrote:
> Hi Kirill,
> 
> On 19 May 2014 17:17, Kirill A. Shutemov
> <kirill.shutemov@...ux.intel.com> wrote:
> > IIUC PyPy uses the syscall in some early prototype and looks like guys are
> > okay to rework it to mmap() if default sysctl_max_map_count will be high
> > enough.
> 
> Yes, we can switch easily if needed.  The syscall is not in any
> "production" version yet.
> 
> Please note that "high enough" in this context means higher than
> 2**20.  We need it high enough to handle regularly 10-20% of all the
> RAM used by each program.  If I count correctly, at 20%, 2**20 fails
> above 20GB.  In general I would suggest to use a default limit that
> depends on the amount of RAM (+swap) available.

Is it nessesary to remap in 4k chunks for you?
What about 64k chunks? Or something bigger?

This way you can scale down required number of VMAs to something more
reasonable.

-- 
 Kirill A. Shutemov
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