mmap64?

mmap64?

[Jason Titus]

We have been doing some work with > 2GB files under x86 linux and have run
into a fair number of issues (instability, non-functioning stat calls, etc).

One that just came up recently is whether it is possible to memory map >2GB
files.  Is this a possibility, or will this never happen on 32 bit
platforms?

Thanks for any help,

Jason.
jason.titus@av.com 
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Re: mmap64?

[Rik van Riel]

On Sat, 22 Apr 2000, Jason Titus wrote:

> We have been doing some work with > 2GB files under x86 linux and have run
> into a fair number of issues (instability, non-functioning stat calls, etc).
> 
> One that just came up recently is whether it is possible to
> memory map >2GB files.  Is this a possibility, or will this
> never happen on 32 bit platforms?

Eurhmm, exactly where in the address space of your process are
you going to map this file?

Rik
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Re: mmap64?

[Jason Titus]

Well, seems like if we are allowing processes to access 3+GB, we should be
able to mmap a similar range.  Also, I don't know too much about the PAE 36
bit PIII stuff but I had thought it might give us some additional address
space...

Jason
jason.titus@av.com

> From: Rik van Riel <riel@conectiva.com.br>
> Reply-To: riel@nl.linux.org
> Date: Sat, 22 Apr 2000 18:30:35 -0300 (BRST)
> To: Jason Titus <jason.titus@av.com>
> Cc: linux-mm@kvack.org
> Subject: Re: mmap64?
> 
> On Sat, 22 Apr 2000, Jason Titus wrote:
> 
>> We have been doing some work with > 2GB files under x86 linux and have run
>> into a fair number of issues (instability, non-functioning stat calls, etc).
>> 
>> One that just came up recently is whether it is possible to
>> memory map >2GB files.  Is this a possibility, or will this
>> never happen on 32 bit platforms?
> 
> Eurhmm, exactly where in the address space of your process are
> you going to map this file?
> 
> Rik
> --
> The Internet is not a network of computers. It is a network
> of people. That is its real strength.
> 
> Wanna talk about the kernel?  irc.openprojects.net / #kernelnewbies
> http://www.conectiva.com/  http://www.surriel.com/
> 
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> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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> 

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Re: mmap64?

[Christoph Rohland]

Jason Titus <jason.titus@av.com> writes:

> Well, seems like if we are allowing processes to access 3+GB, we should be
> able to mmap a similar range.  Also, I don't know too much about the PAE 36
> bit PIII stuff but I had thought it might give us some additional address
> space...

No, the user space address space is not changed.

Greetings
		Christoph

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Re: mmap64?

[Stephen C. Tweedie]

Hi,

On Sat, Apr 22, 2000 at 06:37:29PM -0700, Jason Titus wrote:

> Well, seems like if we are allowing processes to access 3+GB, we should be
> able to mmap a similar range.  Also, I don't know too much about the PAE 36
> bit PIII stuff but I had thought it might give us some additional address
> space...

No, the PAE36 architecture only increases the addressable physical 
memory on Intel CPUs.  It does nothing to change the virtual address
space.

--Stephen
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Re: mmap64?

[Stephen C. Tweedie]

Hi,

On Sat, Apr 22, 2000 at 06:30:35PM -0300, Rik van Riel wrote:
> 
> Eurhmm, exactly where in the address space of your process are
> you going to map this file?

mmap64() is defined to allow you to map arbitrary regions of large
files into your address space.  You don't have to map the whole
file.

--Stephen
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Re: mmap64?

[Rik van Riel]

On Mon, 24 Apr 2000, Stephen C. Tweedie wrote:
> On Sat, Apr 22, 2000 at 06:30:35PM -0300, Rik van Riel wrote:
> > 
> > Eurhmm, exactly where in the address space of your process are
> > you going to map this file?
> 
> mmap64() is defined to allow you to map arbitrary regions of
> large files into your address space.  You don't have to map the
> whole file.

<nitpick>
To be more precise, you _can't_ map the whole file,
which seemed to be what the original poster was asking
for...
</nitpick>

cheers,

Rik
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Re: mmap64?

[Eric W. Biederman]

Jason Titus <jason.titus@av.com> writes:

> We have been doing some work with > 2GB files under x86 linux and have run
> into a fair number of issues (instability, non-functioning stat calls, etc).

Well it's a 2.3.x is a development kernel...

> 
> One that just came up recently is whether it is possible to memory map >2GB
> files.  Is this a possibility, or will this never happen on 32 bit
> platforms?

sys_mmap2 should work just fine...

Eric
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Re: mmap64?

[Jason Titus]

> From: ebiederm+eric@ccr.net (Eric W. Biederman)
> Date: 22 Apr 2000 20:24:13 -0500
> To: Jason Titus <jason.titus@av.com>
> Cc: <linux-mm@kvack.org>
> Subject: Re: mmap64?
> 
> Jason Titus <jason.titus@av.com> writes:
> 
>> We have been doing some work with > 2GB files under x86 linux and have run
>> into a fair number of issues (instability, non-functioning stat calls, etc).
> 
> Well it's a 2.3.x is a development kernel...
> 

This is true.  But I would bet that large file support will be one of the
most noticeable 2.2 -> 2.4 improvements, and it has been a very rough road
so far.  Seems to be working now, and the only two thing that seems to not
work are stat (returns a negative number for >2GB files) and mmap (fails on
2>GB files - perhaps justifiably so...).  I'm just hoping that large file
support will work well by the time 2.4 comes out.  It is one of the main
things that holds Linux back from the enterprise.


>> 
>> One that just came up recently is whether it is possible to memory map >2GB
>> files.  Is this a possibility, or will this never happen on 32 bit
>> platforms?
> 
> sys_mmap2 should work just fine...
> 
I will check that out.

Thanks,
Jason.

> Eric
> 

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