Re: STREAMS: interface versus implementation

Zack Weinberg (zack@rabi.columbia.edu)
Tue, 15 Sep 1998 19:21:25 -0400


On Tue, 15 Sep 1998 23:46:22 +0100 (BST), Alan Cox wrote:
>> STREAMS has been kept out of the kernel because the internal structure
>> and device-driver interface are slow and bloated. Would there be the
>> same opposition to including the user-space interface?
>
>What you put in user space doesnt really matter. Its completely outside
>the kernel and it has no impact on performance of other code or maintenance
>impact (except yours)

Yes. However I think this is one of the things that can't have the right
semantics without kernel help. (Try to implement BSD-compatible SCM_CREDS
support on top of Linux's incompatible sendmsg() option without ever
losing data. It can't be done.)

Which is not to say we should bother with fake streams.

>> in question is already a tty. If done right this thin layer should
>> impose no performance penalty on code that doesn't use it, and should
>> not interfere with future improvements in the kernel.
>
>I question if you need it. The only non-protocol stack use of streams tends
>to be TLI. Alexey Kuznetsov has a user space TLI emulation layer for linux
>if someone wants to beat it back into shape

His code will hopefully be in libc 2.2.

zw

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