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Date:      Thu, 22 Mar 2012 19:57:11 +0000
From:      Eric Saint-Etienne <eric.saintetienne@gmail.com>
To:        Ryan Stone <rysto32@gmail.com>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: malloc pages map to user space
Message-ID:  <CACJX%2B511wZyKVXeYqUQ3v6Uh0ZN83TbBZT7CC6V6N0jTsibD-w@mail.gmail.com>
In-Reply-To: <CAFMmRNxvLz9G73Kn2BXq9WG5-0ZcTN%2BSumawWDzz5DRj=hN4PQ@mail.gmail.com>
References:  <CACJX%2B52DPPYea5k6QxQ6WQ62GEA9YHGr4y=ETUpPArNL83kh5w@mail.gmail.com> <CACJX%2B535YeOwWZodE1w8jiECKbDgyBbZgYDd=M31NwyTMTx83g@mail.gmail.com> <CACJX%2B51Po_RfhUF7Ba1VT0XLfLWQYWFmnRBRcNuDp%2B3nh_AopQ@mail.gmail.com> <CAFMmRNxvLz9G73Kn2BXq9WG5-0ZcTN%2BSumawWDzz5DRj=hN4PQ@mail.gmail.com>

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> If your kernel module creates a device in /dev that implements the
> mmap method, then you don't need to worry about mucking around with
> vm_maps and objects and whatnot. =C2=A0Your mmap method just needs to be
> able to convert offsets into the device into physical memory
> addresses,

Yes I'm aware of this facility, thank you.

> and the vm infrastructure will do the rest for you.

Since this mapping is on the main path of the driver, I'm worried that
the overhead on each access of a page fault and a function call (the
pager associated with a cdev mmap) is too much to bear.

So I'd like to do it the "hard" way which I feel is the most optimized.

Thanks!



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