Date: Fri, 10 Feb 2006 11:59:21 -0800 (PST)
From: Linus Torvalds <torvalds@osdl.org>
To: Oliver Neukum <oliver@neukum.org>
cc: Nick Piggin <nickpiggin@yahoo.com.au>, Andrew Morton <akpm@osdl.org>,
       linux@horizon.com, linux-kernel@vger.kernel.org, sct@redhat.com
Subject: Re: msync() behaviour broken for MS_ASYNC, revert patch?
In-Reply-To: <200602102034.07531.oliver@neukum.org>
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 <43ECDD9B.7090709@yahoo.com.au> <Pine.LNX.4.64.0602101056130.19172@g5.osdl.org>
 <200602102034.07531.oliver@neukum.org>
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On Fri, 10 Feb 2006, Oliver Neukum wrote:
>
> Am Freitag, 10. Februar 2006 20:05 schrieb Linus Torvalds:
> > So we may have different expectations, because we've seen different 
> > patterns. Me, I've seen the "events are huge, and you stagger them", so 
> > that the previous event has time to flow out to disk while you generate 
> > the next one. There, MS_ASYNC starting IO is _wrong_, because the scale of 
> > the event is just huge, so trying to push it through the IO subsystem asap 
> > just makes everything suck.
> 
> Isn't the benefit of starting writing immediately greater the smaller
> the area in question? If so, couldn't a heuristic be found to decide whether
> to initiate IO at once?

Quite possibly. I suspect you could/should take other issues into account 
too (like whether the queue to the device is busy or bdflush is already 
working).

I wouldn't object to that.

		Linus
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