linux-kernel - Re: [take21 0/4] kevent: Generic event handling mechanism.

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Date:	Tue, 07 Nov 2006 07:32:20 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
CC:	David Miller <davem@...emloft.net>,
	Ulrich Drepper <drepper@...hat.com>,
	Andrew Morton <akpm@...l.org>, netdev <netdev@...r.kernel.org>,
	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>
Subject: Re: [take21 0/4] kevent: Generic event handling mechanism.

Evgeniy Polyakov wrote:
> Mmap ring buffer implementation was stopped by Andrew Morton and Ulrich
> Drepper, process' memory is used instead. copy_to_user() is slower (and
> some times noticebly), but there are major advantages of such approach.


hmmmm.  I say there are advantages to both.

Perhaps create a "kevent_direct_limit" resource limit for each thread. 
By default, each thread could mmap $n pinned pagecache pages.  Sysadmin 
can tune certain app resource limits to permit more.

I would think that retaining the option to avoid copy_to_user() 
-somehow- in -some- cases would be wise.

	Jeff


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