From: Christoph Hellwig <hch@lst.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH, RFC] xfs: remove i_iolock and use i_rwsem in the VFS inode instead
Date: Sat, 10 Sep 2016 18:20:37 +0200 [thread overview]
Message-ID: <20160910162037.GA29651@lst.de> (raw)
In-Reply-To: <20160909095148.GH10153@twins.programming.kicks-ass.net>
On Fri, Sep 09, 2016 at 11:51:48AM +0200, Peter Zijlstra wrote:
> Completions and semaphores don't work? And yes, I need to look at that
> cross-release muck, but as is that stuff sets my teeth on edge.
Completions can be used as hacks for some of it - we have two or three
places where we do that in XFS. Using semaphores doesn't seem very
popular. Also I'd much prefer to have a proper lock instead of working
around it, most importantly to get good lockdep support.
And none of that addresses the fact that we're talking about a
shared/exclusive lock here.
> > I think everyone would be better server by accepting
> > that this case exists and finding a place for it in the framework.
> > E.g. for RT trying to boost something that is fully under control
> > of hardware is pointless, but if we have a way to transfer a lock
> > from an owner to a hardware owned state we could at least boost
> > until that handoff happened.
>
> Could be worse than pointless, could indicate borkage.
Yes - pointless is still the best case.
> But yes, once you
> have that event you could propagate it up the PI chain and notify
> things.
>
> IO rarely is deterministic, so having RT tasks in a blocked-on chain
> with it is fail. And yes, there's exceptions etc..
That's often true, but not always. There is things like battery backed
DRAM which is very deterministic, and there is a lot of work going on
to provide relatively deterministic ways of using flash storage.
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prev parent reply other threads:[~2016-09-10 16:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-11 17:10 [PATCH, RFC] xfs: remove i_iolock and use i_rwsem in the VFS inode instead Christoph Hellwig
2016-08-11 21:54 ` Peter Zijlstra
2016-08-18 17:37 ` Christoph Hellwig
2016-08-19 13:27 ` Peter Zijlstra
2016-08-20 6:37 ` Christoph Hellwig
2016-08-22 8:34 ` Peter Zijlstra
2016-09-05 15:12 ` Christoph Hellwig
2016-09-07 7:43 ` Peter Zijlstra
2016-09-08 6:06 ` Ingo Molnar
2016-08-11 23:43 ` Dave Chinner
2016-08-12 2:50 ` Christoph Hellwig
2016-08-12 9:58 ` Dave Chinner
2016-09-05 15:15 ` Christoph Hellwig
2016-09-07 21:45 ` Dave Chinner
2016-09-08 6:54 ` Peter Zijlstra
2016-09-09 1:06 ` Dave Chinner
2016-09-09 8:21 ` Peter Zijlstra
2016-09-09 8:34 ` Christoph Hellwig
2016-09-11 0:17 ` Dave Chinner
2016-09-13 19:42 ` Peter Zijlstra
2016-09-09 8:33 ` Christoph Hellwig
2016-09-09 8:44 ` Peter Zijlstra
2016-09-09 9:05 ` Christoph Hellwig
2016-09-09 9:51 ` Peter Zijlstra
2016-09-10 16:20 ` Christoph Hellwig [this message]
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