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SubjectRe: /tmp in swap space
Date
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Larry McVoy wrote:
>
> : Well, I can give you a real-world example. Because I haven't yet found
> : an OS which has useful mmapping semantics for /dev/zero (namely that I
> : can open /dev/zero and pass a FD to another process and both processes
> : can mmap() the FD and share data via the mmapped region), I end up
> : creating a tmpfile in /tmp for mmapping purposes. Under Linux, this is
> : at least 16 MBytes (because under 16 MBytes I can use ordinary SysV
> : SHM). This tmpfile doesn't need to be saved to disc (not when you have
> : gobs of RAM).
> : So here is a real case where large files with a moderate lifetime (at
> : least a few minutes) are created in /tmp.
>
> I agree with you that it would be nice to be able to share anonymous
> memory between processes (which you can do with clone but that's not an
> answer for unrelated processes).
>
> However, we were discussing TMPFS vs EXT2FS performance. Do you have
> any reason to believe that creating a mapping in TMPFS is any faster
> than one in EXT2FS?

And still if you have plenty of RAM, the Ext2fs version won't write
much to disk. Oh, the bdflush (for simplicty) will write the stuff to
disk eventually, but that's asynchronous, you won't notice much of
this.

Roger.


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