Message-ID: <45507232.7010104@garzik.org>
Date: Tue, 07 Nov 2006 06:46:58 -0500
From: Jeff Garzik <jeff@garzik.org>
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To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
CC: David Miller <davem@davemloft.net>, Ulrich Drepper <drepper@redhat.com>,
       Andrew Morton <akpm@osdl.org>, netdev <netdev@vger.kernel.org>,
       linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@osdl.org>
Subject: Re: [take21 0/4] kevent: Generic event handling mechanism.
References: <11619654014077@2ka.mipt.ru> <45506D51.30604@garzik.org>
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At an aside...  This may be useful.  Or not.

Al Viro had an interesting idea about kernel<->userspace data passing 
interfaces.  He had suggested creating a task-specific filesystem 
derived from ramfs.  Through the normal VFS/VM codepaths, the user can 
easily create [subject to resource/priv checks] a buffer that is locked 
into the pagecache.  Using mmap, read, write, whatever they prefer. 
Derive from tmpfs, and the buffers are swappable.

Then it would be a simple matter to associate a file stored in 
"keventfs" with a ring buffer guaranteed to be pagecache-friendly.

Heck, that might make zero-copy easier in some cases, too.  And using a 
filesystem would mean that you could do all this without adding 
syscalls, by using special (poll-able!) files in the filesystem for 
control and notification purposes.

	Jeff


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