linux-kernel - Re: [take12 0/3] kevent: Generic event handling mechanism.

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Message-ID: <20060823075056.GA18029@2ka.mipt.ru>
Date:	Wed, 23 Aug 2006 11:50:56 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Andrew Morton <akpm@...l.org>
Cc:	Jari Sundell <sundell.software@...il.com>,
	David Miller <davem@...emloft.net>, kuznet@....inr.ac.ru,
	nmiell@...cast.net, linux-kernel@...r.kernel.org,
	drepper@...hat.com, netdev@...r.kernel.org, zach.brown@...cle.com,
	hch@...radead.org
Subject: Re: [take12 0/3] kevent: Generic event handling mechanism.

On Wed, Aug 23, 2006 at 12:07:58AM -0700, Andrew Morton (akpm@...l.org) wrote:
> On Wed, 23 Aug 2006 10:56:59 +0400
> Evgeniy Polyakov <johnpol@....mipt.ru> wrote:
> 
> > On Wed, Aug 23, 2006 at 02:43:50AM +0200, Jari Sundell (sundell.software@...il.com) wrote:
> > > Actually, I didn't miss that, it is an orthogonal issue. A timespec
> > > timeout parameter for the syscall does not imply the use of timespec
> > > in any timer event, etc. Nor is there any timespec timer in kqueue's
> > > struct kevent, which is the only (interface related) thing that will
> > > be exposed.
> > 
> > void * in structure exported to userspace is forbidden.
> > long in syscall requires wrapper in per-arch code (although that
> > workaround _is_ there, it does not mean that broken interface should 
> > be used).
> > poll uses millisecods - it is perfectly ok.
> 
> I wonder whether designing-in a millisecond granularity is the right thing
> to do.  If in a few years the kernel is running tickless with high-res clock
> interrupt sources, that might look a bit lumpy.
> 
> Switching it to a __u64 nanosecond counter would be basically free on
> 64-bit machines, and not very expensive on 32-bit, no?

I can put nanoseconds as timer interval too (with aligned_u64 as David
mentioned), and put it for timeout value too - 64 bit nanosecods ends up
with 58 years, probably enough.
Structures with u64 a really not so good idea.

-- 
	Evgeniy Polyakov
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